Neutral Grounding Reactor(NGR) for Line shunt Reactor
Guru prakash R.
Working Towards a Carbon-Neutral Vision | Specialist in BESS & Renewable Energy
The majority of transmission line faults are temporary. Auto reclosing is used to clear the single-phase-to-ground faults, which are about 70% of the transient faults. The fault arc is usually self-extinguishing after opening the line circuit breakers.
High-speed re-closure of transmission line circuit breakers employed to improve system stability. As the voltage level increases arc de-ionization time increases as well, this will increase the dead time of auto reclose.
To reduce the dead time and having a successful fast reclosing, Line shunt reactors are earthed through Neutral grounding Reactors (NGR). NGR will also helps in reducing the overvoltage due to resonance during single pole operation.
Case study
Without NGR
Fault cleared at 1.35 sec but arc current extinguished after 460 ms , if auto recloser is operated within this time ,fault will occur again then then all the three phase of the line will be tripped.
Reclosing of line done at 1.8 sec, fault is again re ignited because of breaker closed before the arc de-ionization time.
To avoid this scenario either increase the dead time of auto reclose more than 500ms or we have to install NGR on the neutral of the Line shunt rector
With NGR
After installing NGR arc extinguishing time has been reduce to 280ms.
Reclosing done at 1.8 sec, Auto reclose has been successful.
Reference
Guidelines for Selection of Neutral Reactors rating for Shunt Compensated EHV Transmission Lines
Senior Electrical Engineer- at Dornan Engineering Ltd.
2 年Hi Guruprakahs, Thanks for the article. What is the standard reference for disconnect time and the recloser timing? appreciate it if can be explained
ELECTRICAL POWER SYSTEM ENGINEER
4 年congrats on your achievement Guru prakash
Engineering & Management Consultant | Functional&Proposal Consultant | Asset Management | Power System Studies&Design | Innovation | Automation | Telecom&SCADA Expert |Mentor | Auditor ISO QMS&EMS OHSMS
4 年Good discussion on auto recloser timing,NGR Delayed auto-reclosing shall be employed. Dead times of the order of 2s-60s are commonly used. fault arc de-ionisation times and circuit breaker operating characteristics, and power swings on the system decay before reclosing shall be considered. usual practice to incorporate a synchronism check relay into the reclosing system to determine whether auto-reclosing should take place according process live bus/dead line and ive bus/live line reclosing
Battery Energy storage systems Specialist
4 年Guruprakash R. there is a typo.. faulting time and reclosing time to be in seconds i believe. 1.35 seconds is the faulting time , 1.8 seconds is reclosing time and arcing time in milliseconds is fine.
Electrical Power Systems Engineer, specializing in utility transmission protection
4 年Looks good. Is there a typo in the reclose time (1.8 ms)?