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Technical Fields - Technical Writing - New Member

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Earth Fault in DC Control System

03/30/2017 5:34 AM

we have new RTU control panel feeding from solar system 24 V DC solar system panel has earth fault relay.

this relay gives alarm of earth fault,after searching the fault found its comes from HMI(STALH) and RTU (Schneider).

the design engineer insert DC/DC converter to feed RTU and HMI, alarm clear,

he said because the 0 V of RTU and HMI is connected to earth point,dose this consider is good solution,

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#1

Re: Earth Fault in DC Control System

03/30/2017 7:30 AM

If it works, then yes, it is.

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#3
In reply to #1

Re: Earth Fault in DC Control System

04/03/2017 3:22 AM

No other solution which will keep RTU , HMI under monitor as well

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#2

Re: Earth Fault in DC Control System

03/30/2017 9:19 AM

DC supply for protective relay and control systems is often operated ungrounded. Then, if a ground fault occurs, it will not interfere with the operation of the relays/controls, and the ground fault alarm relay will let you know that there is a problem. At that point you should investigate to find and correct the ground fault, before there is a second one that actually causes your DC to fail.

However, some DC-powered equipment connects one of its DC rails to earth ground, which is what your HMI and RTU were doing. The DC-DC converter isolated them, so your main DC system remained ungrounded and eliminated the GF alarm. It's an acceptable solution, but would have been better if the HMI and RTU were available without the solid ground connection to the DC inputs.

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#4

Re: Earth Fault in DC Control System

04/23/2017 6:53 PM

This is depend on configuration, we have to match grounding requirement of power source and load.

Some of solar panel system use grounded system some are not. Load is also the same, some use grounded system such as telecom but some system are not.

If you have different grounding system requirement then you will need to isolate between power source and load which can use converter. You need to ensure that converter is galvanically isolated

Salam,

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