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Upgrading and Renovation Project of a Low-resistance Grounding System

 

In a city of Zhejiang, a system upgrading project from 10 kV to 20 kV has been completely implemented since 2011. Instead, the low-resistance grounding systems are applied. However, the earth fault tripping occurred frequently due to serious accidents arising from birds. The customers in the chemical fiber industry required a lot for the power supply quality, but short-time power failure had great impact on their product quality. Frequent tripping affected the normal industrial production of many enterprises. So the power supply authority often received lots of complaints.
 

Solution:

The original two low-resistance systems are upgraded into intelligent resistance grounding units, so that quick reactors can fulfill accurate compensation and eliminate earth faults in case of transient grounding.
         

Operation Effect:

Comparison of Six 20 kV Lines for Busbar Section #1 in this Substation before and after Renovation (between June 2011 and March 2012)
             

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Before renovation (low-resistance grounding)


After renovation (intelligent multi-mode grounding)

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June 2011


July 2011


August 2011


September 2011


From October 2011 to March 2012


Number of earth fault tripping

5

8

16

3

2

 

During low-resistance grounding, there were 32 earth fault trippings in four months. Since the operation of intelligent multi-mode grounding systems, such tripping occurred twice only in half a year. Apparently, such solution solved the frequent tripping problem and significantly improved the power supply reliability.

 

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