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Experience shows that separate grounding system proved better. The instument system is not subjected to any surge voltage when there is lightning. still grounding resistance could be kept minimum and separate. Also ensure that the voltage between neutral and ground is bare minimum if neutral is...

I am familiar with the protection system for 3.3kv motors. The basic control is VCU (vacuum contactor unit)with back up fuse protection. The following protections are normally provided in the ABB-make REF542+ relays.Similar protections are available in the case of GE -make relays too. 1.0...

I would like to know the type of cable installed. If it is single core armoured cables, then you may have to look into grounding of armours on both sides, that should not be. Thanks, subra

Sepam type of relays could be employed for the generator protection provided all protective functions required for the generator is available like Differential prot Over current prot Earth fault prot REF Neg sequence Over voltage Under voltage Voltage controlled over current etc.. The normal...

Do a simple test to find out whether unbalance current is flowing through any one of the phases for the relay to operate. Put a short on the secondary side of the transformer. Inject low voltage on the primary side and measure through each phase and current through neutrals. This will ensure...

Just check whether the loads are balanced by measuring the phase current and monitor neutral current in the system. Also check neutral current high trip set. Subramanian

You connect a test lamp preferably 230/110V depending on your supply voltage and connect between phase and ground terminal in the extension plug points and confirm the lamp is bright similar to connection bet phase and neutral. Thsi is one of the grounding integerity test I would recommend in a...

Check your instanteneous over current trip set value. It can be adjusted to a higher value so that tripping at the time of starting could be avoided. As long as there is no fault in the motor,the setting can be increased. subramanain

This question is related to one of the "safety concern". Many electrical accidents had taken place without following proper safety standards. The question could be simple but it is very useful to me How to connect welding machine and the object to be welded as per standards. I would like be...

The generator / motor winding power factor or tan delta test was carried out for the 3.3 KV equipments. The generator ratings are 8.0 MW & motor ratings are from 175 KW to 1600 KW. The test referred to as Tip-up test is performed at a number of levels of voltage from 25% to 100% of line to...

We have installed 3.3KV, 8 MW generator sets.Recentlt one testing contractor conducted Double Test (Tan delta) and confirms that the insulation detoriates and require retesting after six months. What is the optimum Tan delta value for healthy generator stator winding? How to compare Tandelta...