Upgrade of the Breakers Control Module in 13 kA EE systems Bozhidar Panev TE-MPE-EE

Overview of the 13kA EE systems There are 32 EE systems located in UA and RR underground areas.

Overview of the 13kA EE systems Interface electronics BCMs Extraction switches DQRQ R=7.7 or 6.6 mOhms

Powering of the holding coil (230 VDC/8 VDC) Holding coil function is to close and to keep the breaker closed In the beginning of the closing process the coil is powered with 230VDC (~22A), then switched to 8VDC (~0.5A). A few parameters of the holding coil: L = 3 H; R = 10 Ohms Due to large inductances, electrical arcs will be present during the commutation of the power sources

New contactor was selected:  More solid contact system  Better contact material - AgSnO2 instead of AgCdO  After 500 cycles  negligible erosion of the contacts was observed Power switching relay (230V/8V) of the holding coil (RL4,6,8,10 in BCMs) Inspection in 2012 found significant erosion of the contacts due to electrical arcs. The risk of burning the holding coil is significant. As a part of preventive maintenance it has been decided to replace these relays in all EE systems (RB and RQD/F) – 256 relays in total.

Revision of the holding coil protection The reason: Two cases in the past when holding coils were overheated and damaged by high current. Question arises: Does the existing circuit breaker provide effective overload protection? Circuit breaker parameters: – “Merlin Gerin” series C60N I = 10A; 400V; 2 – poles; reaction curve  C; Breaking capacity = 10kA

Revision of the holding coil protection Requirements for the protection circuit breaker 1.In case of continuous powering of the holding coil with 230V  adequate reaction in order to save the coil 2.Not to trip during “closing” inrush current 3.React in case of short circuit The analysis shows: C-curve circuit breaker might react with delay of ~300 sec. New circuit breaker was selected and tested: “Schneider”(C60HD) I = 6A; D-curve

Test results for the new selected circuit breaker 200 cycles in P-hall  no trip during “closing” inrush current At the intentionally created fault mode, which provides continuous powering of the holding coil with 230V, the new selected circuit breaker has shown excellent performance –Overload reaction within 10s after closing ~6 sec

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