Fully sealed discharge coil for high-voltage parallel capacitors

FDR3 (35KV) series fully sealed discharge coil, overview of applicability, structure, performance, and characteristics

Model Description


Purpose and Scope of Application
After the FDR3 type 35kV outdoor discharge coil is installed in the parallel capacitor bank of the substation, there must be a discharge device to release the internal charge. For the capacitor bank that implements automatic control switching, it is even more required to release its charge below the safe voltage within the specified time. Therefore, installing a dedicated discharge coil is a necessary technical safety measure for parallel capacitors in the substation.
Considering the safety and reliability of parallel capacitor banks and their supporting equipment during operation, it is recommended to use a widely adopted single star wiring method for capacitor banks. The discharge coils are directly connected in parallel with each phase capacitor, and the secondary winding is connected in an open delta shape, which is connected to the protection relay to form an unbalanced voltage protection circuit as internal protection for the capacitor. If some components inside the capacitor are damaged or malfunctioning, it is required that the unbalanced voltage protection can detect and act on the switch to promptly disconnect the capacitor bank from the power grid. At this time, the discharge coil must have a sufficiently high accuracy level to ensure the performance and implementation of this protection.  
Structure and performance characteristics
1. The box adopts a fully sealed horizontal structure, vacuum dried and oiled, with reliable sealing performance, ensuring complete isolation from the outside air. Its insulation oil compensation method adopts a unique structure and advanced compensation technology. Regardless of the highest and lowest temperature of the environment during operation throughout the year, the pressure inside the box always maintains a slight positive pressure (no more than 0.005Mpa at the highest and no less than 0.001Mpa at the lowest).
2. The sealing performance of the box and ceramic sleeve is reliable, and there is no need for maintenance or replacement of parts during the expected service life, ensuring no oil leakage and explosion-proof function. It is a maintenance free product.
3. The design parameters are reasonable and the accuracy level is high [at 0.9 to 1.3 times the rated frequency and 0 to 100% of the rated secondary load (cos φ=0.8 lag) to ensure accuracy level].
4. Excellent volt ampere characteristics (within 1.9 times the rated voltage range, the iron core shows no obvious saturation trend to ensure linearity).
5. The coverage of supporting capacitors (groups) is wide, simplifying the tedious selection work in the past.
Environmental conditions for use
a. Usage conditions: outdoor and indoor, ambient temperature;
Class A -40~+40 ℃
Class B -25~+45 ℃
Class C -10~+55 ℃
b. Altitude not exceeding 1000m
c. Seismic resistance level: Under the action of an earthquake intensity of 8 degrees, it will be damaged.
d. Installation location: No harmful gases, vapors, or conductive or explosive dust.
e. Maximum wind speed 35m/s

Main technical parameters of FDR3 35kV outdoor discharge coil

Connection method with capacitor (group)



Outline installation dimension diagram

FDR3 type 35kV outdoor discharge coil