[BRTYERY (OP)]

Hello
I have repair relay but i dont understand how does numerical relay work with laptop

[evan_au]

how does a numerical relay work?

In the power industry, numerical relays protect generators, loads and transmission lines from electrical faults. It is like a computer-controlled circuit breaker.

They take measurements of AC power, current, voltage and phase angles, and take preprogrammed actions to cut off the power to faulty parts of the network. They can communicate their actions to other systems, to provide indications in the control room, and coordinate their actions across multiple similar relays. 
See, for example: https://new.abb.com/medium-voltage/distribution-automation/numerical-relays

I have to repair a relay but i don't understand how does a numerical relay work?

If you don't understand how they work, you are definitely not the person to repair them!
- Your previous posts confirms your comment that you don't understand power or electronics

how does numerical relay work with laptop?

There are communication protocols which allows relays to talk to SCADA computers, measurement systems, and other relays.

In the past, these SCADA protocols were all proprietary, so you had to buy all your equipment from one vendor.
Today, these protocols are governed by international standards produced by organisations like ISO and IEC.

In a conversation with an engineer who works on such things, he described the set of standards as being about a meter high stack of paper (I guess that's why they distribute them on paper anymore). In practise, you would get some software to run on your computer which supports these protocols; I am guessing that you would be looking for a freeware version?

To configure a digital relay properly, you need to know the impedances and maximum capacity of your power source and load, to calculate the maximum fault load. You also need to know the capacity and settings of all other relays in the network, so that you power down the smallest part of the network around the fault, without burning out the relay.