Hello everyone,
MV fire pump controllers use vacuum contactors to switching fire pump motors. Surge arrestors are normally required to protect motors from operation overvoltage when motors are stopped by vacuum contactors.
However, NFPA does not require surge arrestors on MV fire controllers...
Hi gentlemen,
Are surge arrestors needed to protect incoming cubicles and transformer or large motor feeder cubicles from switching overvoltage?
IF vacuum breakers are used,ABB 30kV and 6kV switchgear always install surge arrestors. But sometimes Siemens and Schneider do not install the surge...
Hi everyone,
We need to implement differential protection on a 30/6kV 15MVA transformer. Are the CTs for differential protection different from CTs for overcurrent protection? Can we use 5P20 xxx/5A CTs for differential protection? In which case shall we use PX or TP series CTs?
How to decide...
Hi everyone,
Our team is asked to start a 2.5MW/6kV motor with solid state soft starter. The motor is about 300m away from the electric room. The manufacturer of soft starter, Mototronics suggests that a large reactor shall be connected in the circuit to overcome dV/dt problems. I have concerns...
Hi everyone,
We use motor starter c/w fused contactor to control 6kV motors. The 6kV motors and low voltageg 380V motors are all controlled by DCS system.
For the LV motors, smart or intelligent MCC are used,such as Siemens Smart Tiastar MCC.Each MCC cubicles are serial linked to an interface...
Hi everyone,
We will install solid state soft starter to drive 2MW 6KV motors. The soft starter will fed by 13.8kV switchgear via 13.8/6kV captive transformers.
The solid state reduced voltage starter switches on-off during starting and causes harmonic component in the network. I know VFD...
Hello everyone,
We are doing grounding simulation and calculating grounding resistance, touch potential etc. The incoming 60kV step down to 5.5KV and the 60kv system is high resistance grounded and Neutral grounding resitance is rated 200A 10ohm 1s. The maximum fault level at 30KV bus is 25kA...
Gooday,
We have a 30kV switchgear lineup with tied section A and B. The tie breaker is normally open. However, it will be closed for a paralled incoming operation not more than 20 seconds before switching for maintenance . The worst case of fault level on 30kV bus is parallel incoming...
Hello everyone:
We have a 3MW 5.5kV DOL - started motor installed in a concrete plant. The process designer says that it may be started and stopped several times a day. So contactor shall be used to start and stop it. However, the client requires that vacuum circuit breaker will be used to...
