GE DS200TCEBG1B Ethernet interface card

Description of the plant The study of selectivity between medium voltage and low voltage for the plant of Figure 5 is here briefly illustrated. Here are the characteristic parameters of the plant: • characteristics of the supply side network: - rated voltage Un = 20 kV - three-phase symmetrical short-circuit current Ik3 = 12.5 kA - protection against overcurrents IEEE 51: - first threshold: I> ≤ 250 A, t ≤ 0.5 s - second threshold: I>> ≤ 790 A, t ≤ 0.12 s 

• 20/0.4 kV cast resin transformer: - apparent rated power Sn = 1600 kVA - short-circuit voltage Uk = 5,7 % - rated current at the primary It1 = 46 A - rated current at the secondary It2 = 2309 A

It can be noticed that total selectivity

 is guaranteed between X1 and T7 circuitbreakers through an effective setting of S protection. By analyzing the graph, please observe that, to get a good selectivity level with the circuit-breakers X1 and T7 positioned on the load side, Emax air circuit-breaker cannot be selective with the MV protection due to a fault on the LV busbar B1. In fact, if such a fault occurred, both QF2 and QF1 would open

In order to avoid this event

 the most simple solution would be implementing logic or zone selectivity by sending a signal to block the MV release through the zone selectivity outputs present on the Emax trip unit PR123, thus integrating into a single selectivity chain also the MV circuit-breaker. Nevertheless, this is not directly possible, because the voltage of the physical signal used for the zone selectivity on REF542 PLUS shall be comprised between 48 and 240V DC, whereas the zone selectivity connection used on the trip units PR123 (as well as PR122), using a voltage of 24V DC (auxiliary voltage more often used in LV plants). To solve this problem it is possible to use as block signal a signal coming from the modules PR120/K or PR021/K, set to the event “S timing”.

 Company product range

----------------------Ruichang Mingsheng Automation Equipment Co., Ltd----------------------

PLC module, programmable controller, CPU module, IO module, DO module, AI module, DI module

Network communication module,

Ethernet module, motion control module, analog input module, analog output module, digital input module, digital output

Module, redundancy module, power module, relay output module, relay input module, processor module