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Upgrade of Breakers Control Module in 13kA EE Systems

Overview and upgrading process for 13kA EE systems, including extraction switches, holding coil powering, switch relays, and circuit breaker protection, with a focus on improving safety and performance. The text details the challenges faced, preventive maintenance measures taken, and successful implementation of new equipment for enhanced reliability.

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Upgrade of Breakers Control Module in 13kA EE Systems

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  1. Upgrade of the Breakers Control Modulein 13 kA EE systems Bozhidar Panev TE-MPE-EE 27.03.2014

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

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

  4. 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

  5. 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. • 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

  6. 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

  7. Revision of the holding coil protection • Requirements for the protection circuit breaker • In case of continuous powering of the holding coil with 230V  adequate reaction in order to save the coil • Not to trip during “closing” inrush current • 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

  8. 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

  9. Thank You

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