In case 'P' class CT connected burden is greater than rated burden, how will it affect the CT as well as the protection performance in service? Thanks in advance.
Last week, there was total collapse of Pakistan power grid plunging hole of country in darkness for hours.
Any one from Pakistan in this forum who would like to share technical details please!
Transformer neutral is connected to two earth pits independently at the source.
Can someone point me to any international standard on this subject please!
In AC systems there are norms for allowable voltage drop that we follow while sizing the cables.
Typically, from transformer LV terminals to the switchboard - 2% (max) and from LV switchboard to the equipment connected - 3% (max). Thus, the allowable total voltage drop from source to connected...
NFPA 20 says the circuit breaker shall not open if there is temporary loss of motor power supplies for a duration up to 3s.
NFPA 20 allows use contactors for fire pump control. As we all know the contactor auxiliary supply is derived from the same motor supplies and motor contactors are not...
Generator inter-turn protection is not widely employed these days. What could be the reasons!
Is it because of the change in the design of present day design of generators, meaning no two turns are being laid in the same stator conductor slot etc.?
Appreciate your help!
Recently, I have come across 3.3kV VFD output stepped up to 11kV supplying a 7MW motor. The step-up transformer is Y-D with floating neutral on star side.
I am used to Dyn connected captive transformers with the star point high resistance earthed. But, that is without VFD.
Is Y-D with floating...
The current IEC 62271-200 is Edition 2. I understand from IEC website that Edition-2 is under comment round.
How do I get a preview of Ed.3 document!! Thanks
I read that the subject wind farm, commissioned in 2018, is down since 26th Oct'2019 due to failure of under-sea HV cable.
Any details how it failed, is it a straight-through joint or some thing else!!
The grid transformer exploded on 19th Jul'19 at Madison substation belonging to American Transmission Company. I understand the cause is failure of Load Tap changer in the transformer.
Load Tap Changer failures are rare to my understanding. I am used to MR, Germany make On Load tap changers...
IEEE C37.101 on generator ground fault protection advises grounding of one of the line terminals on VT secondary side (and keeping star point ungrounded). This is to avoid maloperation of Generator ground fault protection which is set sensitive in case of high resistance grounded unit...
Has anyone seen the report copy??
I am aware there was fault in one of 500kV lines which triggered the event. But, as we all know from experience such major disruptions involve more than one failure at ground level.
I am curious to have the lessons that the event could offer to us, protection...
Transmission systems face Over voltage issues during grid disturbances when there is loss of major loads, leaving a large no. of unloaded or lightly loaded lines in the system (with associated excess VARs).
How do utilities control the situation? Is tripping of identified transmission lines an...
Hi!
IEC 60034-1 Table-2 gives negative phase sequence capability (I2squared-t) ratings for Synchronous machines. However, I couldn't find reference for squirrel cage induction motors, neither in IEC or IEEE.
I am looking for typical I2squared-t values for HV motors.
I know the capability...
Trip and auxiliary relays of Alstom (now GE grid solutions) conform to vibration resistance class-2 as per IEC 60255-21-1 whereas, others in the market (except Reyrolle which is now part of Siemens) seem to provide relays conforming to Class-1 only.
Any one experienced problems like spurious...
7.2MW, 11kV Synchronous motor is coupled to a compressor through geared hydraulic coupling.
The motor starts as Induction motor. It has been in service for nearly 20-years.
Recently, when it was started the motor current fluctuated as if in a power swing and went beyond the rated starting...
It is standard practice to install test terminal blocks (TTB) in C&R panels.
The CTs etc. wiring is routed to the relays through test terminal block to facilitate relay testing without disconnecting the CT wires at the relay.
Alstom TTB type MMLG01 is most widely used to my knowledge.
These...
