Shanghai Huabang Industrial Business Network - Differential relay

[Differential relay]LCD-3,LCD-3A series differential relay

2026-6-13 19:18:57

LCD-3, LCD-3A series differential relay

[Differential relay]LCD-8,LCD-8A series engine differential relay

2026-6-13 19:18:48

LCD-8, LCD-8A series engine differential relay

[Differential relay]LCD-4 Transformer Differential Relay

2026-6-13 19:18:40

LCD-4 type transformer differential relay

[Differential relay]DCD-2M type differential relay

2026-6-13 19:16:01

1. Overview:
The DCD-2 type is used as a single-phase differential main protection for two winding or three winding transformers, AC generators, and busbars, while the DCD-2M type is used as a starting element for single busbar segmentation and double busbar full differential.

2. Model parameters:

rated value	Action Anza	Rated range of operating current (A)	Reliability coefficient	Action time (ms)	Power consumption (VA)	contact form	Contact capacity (W)
5A 50Hz	60±4	Used for three winding transformers 3-12A (60 ampere turns) for two winding transformers or generators 1.55-12A	5 times the operating current �� 1.35 2 times the operating current �� 1.2	3 times the operating current �� 35	��16	DCD-2 1. Dynamic combination DCD-2M 1. Dynamic combination 1. Dynamic interruption	DC 50W AC 250VA

DCD-2M type differential relay

[Differential relay]BCD-51 type differential relay

2026-6-13 19:15:52

1. Overview:
BCD-51 differential relay is used as the main protection in single-phase differential protection circuits of double winding power transformers and generators. Transistor based, phase comparison and waveform discrimination principle.

2. Model parameters:

rated value			Setting range	Action time (s)	braking coefficient	Locking angle	power consumption
AC current (A)	Frequency (Hz)	DC voltage (V)					Communication (VA)	DC (W)
five one	fifty	two hundred and twenty one hundred and ten forty-eight	0.5-1.5 times the rated current	2 times the operating current �� 40	>2	>70°	��2VA	220V ��12 110V ��7 48VV ��5

BCD-51 differential relay

[Differential relay]LCD-1A type differential relay

2026-6-13 19:15:43

1. Overview:
LCD-1A differential relay is used for single-phase differential protection circuit of AC generator as protection. Rectification type, corresponding comparison principle.

2. Model parameters of LCD-1A differential relay:

Rated current (A)	Rated frequency (Hz)	Current setting range (V)	Action time (ms)	braking coefficient	Locking angle	Power consumption (VA)	Contact capacity
five one	fifty sixty	0.5-1 times the rated current	3 times the operating current �� 35	>3	��±60°	��1.5	220V,0.5A DC has feelings 30W AC 40VA

4. Installation dimensions:

5. Wiring diagram:

LCD-1A type differential relay

[Differential relay]DCD-5A type differential relay

2026-6-13 18:35:48

1 Overview

DCD-5A differential relay (hereinafter referred to as relay) is used in single-phase protection wire bars of two winding or three winding power transformers as the main protection.
1.2 Working conditions of relays
a. The ambient temperature is -25-+40 ��;
b. Atmospheric pressure: 80-106kPa (altitude not exceeding 2000m);
c. The relative temperature of the air is 45% to 75%;
d. The reference value for the working position is vertical, with a tolerance of 2 ° deviation in any direction;
e. There should be facilities to protect against wind, sand, rain, and snow, as well as an environment free from corrosive and explosive gases;
f. No strong vibration or impact
g. There should be no significant external magnetic field influence in any direction around the usage location.

Basic structure and working principle of DCD-5A differential relay:

2.1 Basic Structure
The relay consists of a highly sensitive and reliable electromagnetic actuator with a pair of dynamic contact points and an intermediate speed saturation converter.
The actuator is an electromagnetic relay, which is used as
Export components.

Figure 1 Schematic diagram of the distribution of windings on magnetic conductors

The magnetic conductor of the inverter is composed of "E" shaped magnetic plates stacked together. The working winding (differential winding), balance winding I, and balance winding II are placed on the middle column of the magnetic conductor. The secondary and braking windings are divided into two halves and wound on the two side columns respectively. The distribution of windings on the magnetic conductor is shown in Figure 1. Internal wiring of relays and principle wiring for protecting three winding power transformers
As shown in Figure 2. Due to its balanced winding and tap every turn for adjustment, it is used to eliminate the effect of unbalanced current caused by inconsistent current transformer ratios and other reasons. Having two balanced windings enables relays to be used to protect three winding power transformers.
The operating current, balancing effect, and braking characteristics can be tuned over a wide range of turns through the working winding, balancing winding, and braking winding.

2.2 Basic Principles
When a short circuit passes through the current in the braking winding, the magnetic conductor of the inverter is saturated, thus deteriorating the current induction conditions from the differential winding and balance winding to the secondary winding while ensuring the same braking characteristics. The two halves of the secondary winding and braking winding are connected in such a way that the potential in the two windings is caused by the magnetic flux of the working winding. In order to change the saturation degree of the magnetic conductor of the inverter, the number of turns of the braking winding is made adjustable.
The use of inverters can simultaneously prevent excitation inrush current and relay misoperation during no-load closing of power transformers.
The foot actuator connected to the secondary winding of the inverter. And specify its operating voltage and operating current. The operating voltage reflects the working magnetic flux density of the inverter, and the operating current determines the power distribution ratio of the inverter, while meeting the requirements of universality in production. The characteristic of this type of actuator is that its coil is sufficiently inductive, and there are significant high-order harmonics in the secondary induced potential when the inverter is saturated. Therefore, this type of actuator is a good high-order harmonic filter, which basically reflects the fundamental wave of the inverter's working magnetic flux density.
The schematic wiring diagram of DCD-5A differential relay is shown in Figure 2.

Figure 2 Schematic wiring diagram of relay internal and maintaining three winding power transformer

Main technical performance and parameters of DCD-5A differential relay
3.1 Rated value
Rated current 5A, rated cycle rate 50Hz.
When there is no DC component, the relay starts to operate with an ampere turn Awo of 60 ± 4.
When used to protect a three winding transformer, the operating current of the relay can be set within the range of 3-12A (AWo=50), and for the minimum setting value of the operating current, its maximum balance coefficient is close to 2.
When used to protect a two winding transformer, the operating current can be adjusted within a finer range of 1.55-12A (Awo=60).
3.4 Braking coefficient
The operating current of the relay in the working winding can change the current in the braking winding (the ratio when AWT=280).
a. For maximum setting action current above 0.18;
b. For 3A, the setting action current is below 0.63;
Figure 3 shows the relationship curve of Awp=f (AWr) when there are different phase shift angles between the braking current and the operating current. From Figure 3, it can be seen that the relationship between the braking coefficient and the phase shift angle between the operating current and the braking current cannot exceed these two characteristic curves.
3.5 Reliability coefficient
The reliability coefficient of the relay should not be less than 1.35.
When the differential relay operates, its operating current is ICP, and the sine operating current of the actuator is iCP. Then, rotate the pointer and tighten the balance spring to make the operating current of the relay 5ICP. Measure the corresponding sine operating current ICP5 of the actuator, and calculate the reliability coefficient according to the following formula.
Kh=Icp1/Icp5

Figure 3 Relationship curve of AWp=f (AWr) between braking current and operating current with different phase shift angles

In the same situation, when the operating current of the differential relay is 2ICP, the above ratio is not less than 1.2.
When the operating current is 3 times that of 3.6, the operating time of the differential relay shall not exceed 0.035s.
3.7 Efficiency consumption
At rated current, the single-phase power consumption of the relay should not exceed the following specifications.
a) Under normal circumstances, when all the turns of the braking and balancing windings of the inverter are connected, it should not exceed 8.5VA.
b) When there is a fault in the area, the braking, balancing, and number of turns of the working winding of the inverter should not exceed 20VA.
Under normal circumstances, the working winding, braking winding, and balancing winding of the relay can pass a current of 10A for a long time.
3.9 Contact Performance
The relay contacts should be able to disconnect a DC circuit with a voltage not exceeding 250V and a current not exceeding 2A, and a capacity of 50W inductive load (time constant of 5 ± 0.75ms). Under this specified load condition, the relay should operate reliably 1000 times.
3.10 Mechanical lifespan
The mechanical lifespan of the relay is 104 times.
3.11 The conductive circuits of the relay connected together to the ground (or the exposed non-conductive metal parts of the insulation shell) and the conductive circuits that are not electrically connected should withstand an AC test voltage of 2KV (effective value) 50Hz for 1 minute without insulation breakdown or flashover.
3.12 The relay can withstand an impulse voltage of 5kV without insulation damage thereafter.
The weight of the 3.13 relay is approximately 5kg.
The winding data of DCD-5A differential relay is shown in Table 1.

winding	Winding data	Core cross-sectional area	remark
work	Wp=20 turns 1.81 double yarn wrapped copper wire	S=1.25cm2 (Side pillar)	Each winding Tap as shown in Figure 2
Balance I and II	WY1=WY2=19 turns 1.81- Double yarn wrapped copper wire
second	2 × W2=48 turns 1.45 double yarn wrapped copper wire
braking	2 × Wz=2 × 14 turns 1.81- double yarn wrapped copper wire
Execution element	2 × W 2 × 380 turns QQ-0.5 enameled copper wire	S=2.64cm2	Two coils in parallel

The relay structure code is A32K, and the external dimensions and installation dimensions are shown in Figure 5.

4. Use and Maintenance
4.1 Setting of working winding, balancing winding and braking winding
Open the shell cover to adjust the working winding, balance winding, and brake winding. The working winding, balancing winding, and braking winding all have taps that can meet the requirements of various setting values. The number below the relay setting board represents the corresponding winding turns. The balanced winding and the working winding are each divided into two sections for tuning. This design can use fewer taps to obtain more combinations of turns, thus making the tuning range wide and precise. Each tuning board has two tuning screws, each of which can be tuned within its own range. The sum of the numbers marked at the tuning positions of the two screws is the number of turns for the winding. (It should be noted that when two set screws on the same setting board are not set within their respective ranges or are not connected, the winding will be disconnected.)
When a circuit breaker is used to protect a three winding power transformer, two balanced windings should be applied and connected to the two arms of the circulating current circuit, so as to balance the effect of unbalanced currents in the three circulating current circuits. When used to protect a two winding power transformer, only one balanced winding is required. In the case of a large unbalanced current, the balanced winding is connected to the circulating current circuit. When the unbalanced current is small or used to protect the AC generator, the balanced winding can be connected to the working circuit to expand the range of setting values. The role of the balanced winding can be represented by the balance coefficient determined by the ratio of the secondary currents of two current transformers. The actual balance coefficient should be calculated based on the number of turns connected to the winding. According to the circuit in Figure 4, I1 and I2 respectively represent the secondary currents of two current transformers, and I1 is greater than I2. The balanced winding is usually connected to the circulating arm with the smaller current. When the synthetic magnetization force of the working circuit is zero, the effect of unbalanced current is completely eliminated, thus obtaining the following equation:
(I1-I2) WP I2 WY=0 (1) or I1WP=I2 (WP+WY) (2)
The equilibrium coefficient KY is: Ky=I1/I2=(Wp+Wy)/Wp

The initial action of the relay's ampere turns can be adjusted within a small range using potentiometer W. When adjusting, first loosen the fastening nut, and then use a "-" shaped screwdriver to adjust the potentiometer handle.
During the operation of the relay, attention should be paid not to change the position of the pointer on the nameplate.

5 Supply completeness
Complete set of work supply
5.1 Certificate of Conformity.
5.2 User Manual (one copy for batch orders from the same subscriber).
5.3 Install attachments.

6 Ordering Instructions
Please specify when placing an order
6.1 Name and model of relay.
6.2 Rating of Relays.
6.3 Relay appearance structure code.
6.4 Order quantity.

Figure 4: Schematic wiring diagram of relays used to protect two winding power transformers

Figure 5 Appearance and installation dimensions of DCD-5A differential relay

[Differential relay]DCD-2 type differential relay

2026-6-13 18:35:39

1 Purpose
DCD-2A differential relay (hereinafter referred to as relay) is used as the main protection in single-phase differential protection lines of two winding or three winding power transformers and AC generators.
Relays can prevent transient currents that occur in non fault states. For example, when a power transformer is closed without load or after a transient short circuit is cut off, there is a large excitation inrush current when the voltage is restored, and its instantaneous value often reaches 5-10 times the rated current; At this time, the differential protection should not malfunction, but it can quickly cut off the fault when a short circuit occurs within the area.

2 Structure and working principle
2.1 Structure
The relay consists of a highly sensitive and reliable electromagnetic actuator with a pair of dynamic contact points and an intermediate speed saturation converter. The actuator is an electromagnetic relay, which is used as an outlet component in the relay.
Intermediate speed saturated converters have short-circuit windings and balanced windings, which constitute some of the main technical performance of differential relays, such as the performance of DC bias characteristics to eliminate unbalanced current effects in autotransformers.
The magnetic conductor of the inverter is composed of stacked "E" magnetic plates, with balanced windings I and II and short-circuit windings. In addition, the short-circuit winding on the middle column is connected to the short-circuit winding on the right side column through a ceramic potentiometer, and the secondary winding is placed on the other side column of the magnetic conductor. The distribution of windings in the magnetic conductor is shown in Figure 1. The internal wiring of the relay and the principle wiring diagram for protecting a three winding power transformer are shown in Figure 2. Due to its balanced winding and tap every turn, it is easy to adjust and eliminate the effect of unbalanced current caused by inconsistent current transformer ratios. Having two balanced windings enables relays to be used to protect three winding power transformers.
The action current and balancing effect can be adjusted within a wide range by adjusting the number of turns of the working winding and balancing winding. The DC bias characteristic can be adjusted by changing the resistance of the ceramic potentiometer of the relay.
The structural form, appearance, installation dimensions, and terminal wiring of the relay are shown in Figure 6.
2.2 Principle
The basic principle of a relay is to use the non periodic component of the transient current during non fault conditions to magnetize the magnetic conductor of the inverter, increase its saturation level, and thus avoid the effect of excitation inrush current and unbalanced current during transient faults. The corresponding characteristic curve is the DC bias characteristic curve cluster �� 2f (K). Differential circuit connected to the working winding for protection; The balanced winding can be connected to the loop or working circuit according to actual needs.
The inverter with short-circuit winding is characterized by the specialized use of non periodic current to magnetize the magnetic conductor. Figure 3 shows the electromagnetic process inside the magnetic conductor. When the power transformer is closed under no-load, the excitation inrush current with a large instantaneous value flows through the working winding, and the waveform of the inrush current has a magnetic flux biased towards the time axis. They produce two different reactions in the short circuit group. Under the action of DC magnetic flux, the magnetic conductor quickly saturates, greatly reducing the magnetic permeability. This greatly deteriorates the electromagnetic induction conditions between the working winding and the secondary winding, thus significantly increasing the operating current of the relay, which is called DC bias phenomenon.

When there is a transient short circuit and the short-circuit current contains non periodic component currents, the same effect is also produced, which can prevent misoperation when the transient short circuit is cut off and the voltage is restored. The DC bias characteristic of the relay is represented by the curve family of Figure 4, denoted as f (K).
Among them, ��=Icp/Icpo, the multiple of the operating current, is the ratio of the AC operating current with a DC component to the AC current with a DC component equal to zero.
K=I=/Icp�� The offset coefficient, which is the ratio of the DC component to the corresponding AC operating current, represents the degree of deviation of the current waveform from the time axis.
The above ��=f (K) is the static characteristic of the relay, which was obtained by testing the simultaneous application of AC and DC currents in the working winding. DC current does not change with time, while the value of non periodic component current gradually decays with the increase of time.
In order to achieve better speed saturation characteristics, a higher working magnetic flux density Bcp was selected in the design of the inverter. However, to ensure the necessary capacity for reliable relay operation, it is stipulated that the reliability coefficient KH should not be less than 1.35 when the operating current of the relay is 5 times the starting value.
The working magnetic flux density of the inverter is determined by the weight of the magnetic material and the initial operating voltage and current. The operating voltage reflects the operating magnetic flux density of the inverter; The action power determines the power distribution ratio of the inverter and meets the requirements of universality in production. The characteristic of this type of actuator is that its coil is inductive. In the case of inverter saturation, the secondary induced potential contains significant high-order harmonic filters. Therefore, this type of actuator is a good high-order harmonic filter, which basically reflects the fundamental wave of the inverter's working magnetic flux density.
The principle wiring of the relay is shown in Figure 2.

Technical performance and parameters of DCD-2 differential relay:
3.1 Rated value
Rated current 5A, rated power 50Hz.
When there is no DC component, the relay starts to operate with an ampere turn Awo of 60 ± 4.
When used to protect two winding power transformers or AC generators, the operating current can be set within the range of 3-12A (Awo=60). For the minimum setting value of the operating current, the maximum balance coefficient is close to 2.
When used to protect two winding power transformers or AC generators, the operating current can be set within the range of 1.55-12A.
The DC bias characteristic of the 3.5 relay is ��=f (K), which can be continuously adjusted by changing the resistance value of the ceramic disc variable resistor.
When the offset coefficient K is 0.6, the error of the relative operating current coefficient of the DC bias magnetic characteristics at each setting position does not exceed -8% to+20%. The reliability coefficient of the relay should not be less than 1.35.
When the differential relay operates, its operating current is lCPO, and the corresponding sine operating current of the actuator is icpl. Then, rotate the pointer and tighten the balance spring to make the operating current of the relay 5Icp and measure the corresponding sine operating current icp5 of the actuator. Calculate the reliability factor according to the following formula: Kn=Icp5/icp1.
In the same situation, when the operating current of the differential relay is 2ICP, the above value is not less than 1.2.
When the operating current is 3.7 times, the operating time of the differential relay shall not exceed 0.035 seconds.
When all the turns of a balanced winding and a working winding of the inverter are connected, there is a fault in the protection zone and the current is equal to 5A. The single-phase power consumption of the relay does not exceed 16VA.
Under normal circumstances, the transformation ratio error of the current transformer is fully compensated (the magnetization force of the inverter working circuit is balanced, and the magnetic flux in the magnetic field is moldy). The next work involves winding molybdenum and balancing thin wires, which can withstand a current of 10A for a long time.
It is a test conducted by applying direct current when all turns of the balanced winding and working winding are connected.
The DC resistance of the working winding or each balanced winding should not exceed 0.05 ��.
3.11 Contact Performance
The relay contacts should be able to disconnect inductive loads with a voltage not exceeding 250V and a DC not exceeding 2A, and a capacity of 50W (time constant)
For a DC circuit of 5 ± 0.75ms, the relay should reliably operate 1000 times under this specified load condition.
3.12 Mechanical lifespan
The mechanical lifespan of the relay is 104 times.
3.13 The conductive circuits of the relay connected together to the ground (or the exposed non-conductive metal parts of the insulation shell) and the conductive circuits that are not electrically connected should be able to withstand an AC test voltage of 2kV (effective value) 50Hz for 1 minute without insulation breakdown or flashover.
3.14 The relay can withstand an impulse voltage of 5kV without insulation damage thereafter.
The weight of the 3.15 relay is approximately 6kg.
The winding data of the 3.16 relay is shown in Table 1.

Winding	Winding data	Core cross-sectional area	remark
work	Wp=20 turns 1.56-SBEC double yarn wrapped copper wire	S=1.25cm2 (Side pillar)	Each winding tap See Figure 2
Balance I and II	WYl=WY2=19 turns 156-SBEC double yarn wrapped copper wire
second	W2=48 turns 1.0-SBEC double yarn wrapped copper wire
Execution element	2W=2 × 380 turns QQ-0.51 enameled copper wire	S=2.64cm2	Two coils in parallel

4 Working conditions
4.1 The ambient temperature ranges from -25 �� to 40 ��.
4.2 Atmospheric pressure: 80-106kPa (altitude not exceeding 2000 meters).
4.3 The relative temperature of the air is 45% to 75%.
The reference value for the working position is vertical, with a tolerance of 2 ° deviation in any direction.
4.5 There should be facilities to protect against sandstorms, rain, and snow, as well as an environment free from corrosive and explosive gases.
4.6 No strong vibration or impact.
4.7 There should be no severe external magnetic field influence in any direction around the usage location.

5. Use and Maintenance
5.1 Setting of working winding and balancing winding.
Open the shell cover to adjust the working winding and balance winding. The working winding and balance windings I and II have taps that can meet the requirements of various setting values. The number below the relay setting board represents the corresponding winding turns. Each winding is divided into two sections, and this design allows for fewer taps to obtain more combinations of turns, thereby enabling a wide range of tuning without losing its precision. There are two setting screws on each relay setting board, and each setting screw can be set within its own range. The sum of the numbers marked at the set positions of the two screws is the set number of turns of the winding.
It should be noted that when two setting screws on the same setting board are set within their respective ranges or not connected, the winding is disconnected.
5.2 Adjustment of magnetic characteristic curve
When setting the magnetic assistance characteristic curve, the relay core needs to be removed, and then the three large screws that lock the ceramic disc variable resistor on the magnetic assistance characteristic signboard need to be loosened (do not unscrew, just loosen them), so that the knob can rotate freely. Rotate the knob to adjust the magnetic characteristic curve.
5.2.1 Curve tuning according to regulations
The relay has four curves: A, B, C, and D. These four curves have been carefully debugged according to technical requirements before the relay leaves the factory, so simply align the arrow on the knob with the desired setting point.
5.2.2 Special Requirements Setting
If the curve needs to be adjusted within the range between curves A and D, but not on curves A, B, C, and D, the following method can be used for adjustment:
1) Determine the �� value of the curve at K=0.6 based on the required �� 2-f (K) curve.
2) Determine the required DC current value to be added during the experiment.
Apply current between terminals �� and ��, set the working winding to 20 turns and the balance winding to 19 turns, and then measure the initial sinusoidal current value lCPO. Calculate the DC current I=KICPO=0.6Icp based on K=0.6 and
3) Determine the position of the disk variable resistor
Calculate the AC operating current ICP=�� ICPO when there is a DC component, as specified in Article 1; ICPO is measured according to Article 2). Set the working winding and balance winding to 20 turns and 19 turns respectively, and add the previously calculated DC current value I and AC operating current ICP between terminals �� and ��. Adjust the variable resistor to make the relay's operating current ICP.
4) If precise tuning is required, the indication of the variable resistor knob can be temporarily kept at the previously set position, and then the subsequent tuning steps from point 2) can be repeated until the tuning position of the variable resistor no longer changes. Due to the change in resistance of the variable resistor, the initial action ampere turns can vary within a small range.
After setting the magnetic characteristic curve, the three locking screws should be evenly tightened.
When a relay is used to protect a three winding power transformer, two balanced windings should be applied and connected to the two arms of the circulating current circuit, so as to balance the effects of unbalanced currents in the three circulating current circuits. When used to protect a two winding power transformer, only one balanced winding needs to be applied. In the case of a large unbalanced current, the balanced winding is connected to the circulating current circuit. When the unbalanced current is small or used to protect the AC generator, the balanced winding can be connected to the working circuit to expand the range of setting values. The role of the balanced winding can be represented by the balance coefficient determined by the ratio of the secondary currents of two current transformers. The actual balance coefficient should be calculated based on the number of turns connected to the winding. According to the circuit in Figure 6, I1 and I2 respectively represent the secondary currents of the two current transformers, and the balanced winding is usually installed on the current arm. When the synthetic magnetization force of the working circuit is zero, the effect of unbalanced current is completely eliminated, thus obtaining the following equation:

(I1-I2) WP-I2Wr=0 or I1WP=I2 (WP+Wr) (1)
The equilibrium coefficient KY is Ky=I1/I2=(Wp+Wr)/Wp (2)

The initial action of the relay's ampere turns can be adjusted within a small range using potentiometer W. When adjusting, first loosen the fastening nut, and then use a straight screwdriver to adjust the potentiometer handle.
During the operation of the relay, care should be taken not to change the position of the pointer on the nameplate.

6 Ordering Instructions
6.1 Name and model of relay.
6.2 Rated value of relay.
6.3 Number of relays.

Figure 1 Distribution of winding in magnetic conductor Wp Working winding Wr Balanced winding I, II W2 Secondary winding Wko Short circuit winding

Figure 2 Schematic wiring diagram of internal wiring of relay and protection of three winding power transformer

Figure 3 Schematic diagram of magnetization process inside the magnetic conductor
Wp working winding Wy1 Wy2- balanced winding I, II W'ky W ''ky - short-circuit winding W2- secondary winding
P-magnetic flux generated by working winding oky magnetic flux generated by short-circuit winding
O=DC magnetic flux generated by non periodic component current flowing through the working winding

Figure 4: Cluster of magnetic assist characteristic curves and adjustment range of DCD-2 differential relay (R: 0~12W)

Figure 5 LH current transformer BY transformer WP differential winding WY balanced winding

Figure 6 Appearance and installation dimensions of DCD-2 differential relay

[Differential relay]BCH-2 type differential relay

2026-6-13 18:34:01

BCH-2 type differential relay

1 Purpose
BCH-2 differential relay is used for single-phase differential protection of two winding and three winding power transformers, as well as AC generators.
Relays can prevent protection from non selectively acting due to unstable transient currents caused by non fault conditions (such as short-circuit currents or transformer no-load closing).

Overview of Structure 2
This relay consists of an electromagnetic current relay DL-11 and an intermediate speed saturation converter.
Relays have short-circuit windings, which constitute some of the main technical properties of differential relays, such as the performance of DC bias characteristics to eliminate unbalanced current effects in autotransformers.
All windings of the speed saturation converter are made with taps, so that the parameters of the relay can be adjusted step by step.
When using BCH-2 type relays to protect power transformers, the number of turns of the balanced winding is selected based on the condition that when a crossing short circuit occurs, the number of turns of all windings should be equal.
When a relay is used to protect a two winding transformer, the operating current can be adjusted within a more detailed range, as two balanced windings can be utilized at this time.
The inverter and the actuator are placed in the same housing. In order to facilitate separate verification, adjustment, and testing of the inverter characteristics, the coil of the actuator is connected to the secondary winding, balance winding, and working winding of the inverter through a connecting plate. Therefore, the corresponding circuit can be connected or disconnected during adjustment and testing.
Do not change the position of the pointer on the relay nameplate (do not leave the nameplate scale) or move the spring fixing screw without moving the pointer. This will deteriorate the ability to avoid the influence of non periodic components of magnetizing current or unbalanced current, or reduce the reliability coefficient of the relay when a short circuit occurs within the protection zone. The schematic diagram 1 of the inverter wiring and the external wiring diagram of the relay for protecting the three winding power transformer are shown in Figure 2.

Figure 1

Figure 2

Figure 3 DC magnetic assist characteristic curve

3 Technical data
3.1 Rated current 5A, rated frequency 50Hz.
The starting action of the relay is 60 ± 4 ampere turns.
3.3 The DC magnetization characteristic curve of the relay (as shown in Figure 3) ��=f (K) should be able to be adjusted in sections;
The ratio of the K-DC component to the corresponding AC operating value.
When �� - has a DC component, the ratio of the AC operating current of the relay to the AC operating current without a DC component.
Figure 3 shows the ��=f (K) curve cluster when the short winding is connected to different turns. When K=0.6, the corresponding �� value for each short-circuit coil tap should comply with the following regulations:

Short circuit winding tap position: ��: A-A, 1.6 ± 0.13; B-B��3±0.24�� C-C��5±0.38�� D-D��7±0.56��
3.4 The reliability coefficient should not be less than 1.35, and the reliability coefficient should be determined according to the following method: assuming the operating current of the relay is Id, the corresponding operating current of the DL-11 type relay is i1; Then rotate the pointer and tighten the balance spring to make the operating current of the differential relay 5Id. Measure the corresponding operating current i5 of the actuator, and calculate the reliability coefficient according to the following:
KK=
When the operating current is 3.5 times, the operating time of the differential relay shall not exceed 0.035s;
When the voltage does not exceed 220V and the current does not exceed 2A, the breaking capacity of the relay contacts in a DC inductive load (time constant of 5 × 10-3s) circuit is 50W.
At rated current, when the balance winding (1 or II) and the number of turns of the working winding of the relay are all connected, the single-phase power consumption of the relay should not exceed 16VA
When the temperature of the surrounding medium is+40 ��, the working winding and a balancing winding of the relay should be able to pass 10A current for a long time, and the temperature rise should not exceed 60K.
3.9 Dielectric strength: Each circuit of the relay should withstand an AC voltage of 50Hz and 2kV for 1 minute without breakdown or flashover between the exposed non charged metal parts.
3.10 When all the turns of each winding are connected and the short-circuit winding is connected at position A-A, their impedance values are shown in Table 1.

Winding	At the following current values (A) and impedance Z (��)			DC resistance (��)
Winding	three	five	ten	DC resistance (��)
Work	zero point three two	zero point two eight	zero point one nine	zero point zero four
Balance \|\|\|	zero point three	zero point two seven	zero point one eight	0.042-0.044

3.11 The weight of the relay shall not exceed 4KG
3.12 The winding data of the relay is shown in Table 2

Winding	Winding data	remark
Work	Wp=20 turns with a diameter of 1.56
Balance I, II	Wy=19 turns (per piece) �� 1.56
Short circuit (center pillar)	W'Kz=28 turns with a diameter of 1.45
Short circuit (side pillar)	W "Kz=56 turns with a diameter of 1.45
second	W2=48 turns with a diameter of 1.0
Execution element DL-11 type relay	2W, 2 x 500 turns, with a diameter of 0.38	Two coils in parallel

3.13 The appearance and opening size of the relay are shown in BCH-1 type.

4 Ordering Instructions
The purchase order should specify:
4.1 Model and name of relay.
4.2 Wiring method (pre board wiring or post board wiring).
4.3 Order quantity.

[Differential relay]BCH-1 type differential relay

2026-6-13 18:33:51

1 Purpose
The BCH-1 differential relay has a braking winding that can provide single-phase differential protection for two winding and three winding power transformers.

Overview of Structure 2
The BCH-1 differential relay consists of a DL-11 electromagnetic current relay (actuator) and an intermediate fast saturation converter (hereinafter referred to as the converter).
Relays have braking windings, which constitute some of the main technical properties of differential relays, such as braking characteristics, avoidance of excitation inrush current characteristics, and performance of autotransformers to eliminate unbalanced current effects.
The magnetic conductor of the inverter is a three column iron core, composed of several sets of "mountain" shaped magnetic plates stacked together. The working winding and balance winding I and II are placed on the middle column of the magnetic conductor, while the braking winding and secondary winding are divided into two parts and placed on the two side columns of the magnetic conductor. The connection method should ensure that there is no mutual induction between the braking winding, secondary winding, and balance winding I and II. The induced potential in the secondary winding is generated by the magnetization of the working winding. In order to change the degree of saturation of the inverter magnetic conductor, the number of turns of the braking winding can be changed.
The inverter can prevent both excitation inrush current and relay misoperation during power transformer fault crossing. Inverter and actuator
The components are placed in a casing, and the relay can be wired in front of and behind the board during installation. The schematic diagram of the inverter wiring is shown in Figure 1, and the external wiring of the relay for protecting the three winding power transformer is shown in Figure 2.
The setting plug on the corresponding hole of the inverter connection board can be used to adjust the operating current, balance coefficient, and braking coefficient. The number on the hole represents the number of turns of the inserted winding when it is set in that hole.

Figure 1

Figure 2

3 Technical data
3.1 Rated current 5A, rated frequency 50Hz.
3.2 When there is no braking, the starting action of the relay is AWo=60 ± 4.
When used to protect a three winding power transformer, its operating current can be set within the range of 3A to 12A (AWo=60),
For the minimum setting value of the action, its maximum balance coefficient is close to 2.
When used to protect a two winding power transformer, its operating current can be set within the range of 1.55A to 12A.
The braking coefficient Kz determined by the ratio of action current to braking current can vary widely, as shown in Figure 3
The characteristic AWp=f (AWz) is its limit range, which is related to the phase angle between the operating current and the braking current, but regardless of the angle
It should not exceed the range of the curve.
3.5 Reliability coefficient (the sine current of the relay when one action current is equal to 5IDZ and the sine current of the relay when one action current is equal to IDZ)
The ratio of operating currents shall not be less than 1.35.
The action time of the differential relay with 3 times the action current shall not exceed 0.035s.
3.7 The relay has a dynamic contact, and in a DC circuit with inductive loads, the breaking capacity of the contact is 50W when the time constant is not greater than 5 × 10-3s, the voltage is not greater than 220V, and the current is not greater than 2A.
3.8 Under normal operating conditions, when the current is 5AK, the single-phase power consumption of the relay shall not exceed 8.5VA when the brake winding balance winding of the inverter is fully turned on.
The working, balancing, and braking windings of the 3.9 inverter can pass a current of 10A for a long time.
3.10 Dielectric strength: The circuit of the relay should be able to withstand an AC voltage of 2kV, 50Hz for 1 minute without breakdown or flashover between the exposed non charged metal parts.
The weight of the 3.12 relay shall not exceed 4kg.
The winding data of relay 3.13 is shown in Table 1.

Winding	Winding data	Remarks
work	Wp=20 turns with a diameter of 1.81
Balance I, II	Wy=19 turns (per piece) with a diameter of 1.81
braking	2 × Wz=2 × 14 turns with a diameter of 1.8l
second	2 × W2=2 × 24 turns, with a diameter of 1.45
Execution element DL-11 type relay	2 × W=2 × 500 turns, with a diameter of 0.38	Two coils in parallel

The appearance and opening size of the 3.14 relay are shown in Figures 4 and 5.

Figure 3 Braking characteristic curve

Figure 4

Figure 5

4 Ordering Instructions
4.1 Relay name and model.
4.2 Wiring method (pre board wiring or post board wiring).
4.3 Order quantity.