Parallel Operation of Power Plant With Grid

Where is your plant located?

hire a professional engineer

hi freind,

why don't u add some HT switch gears.

to make eather on changeover

Hello,

One of the problems I have come across is plans having captive power plants being unable to island themselves in the event of a grid outage. If they are not having much of an incentive to export, they prefer to stay islanded from the grid and maintain their own frequency (an added advantage to that is that you can maintain a very healthy frequency and run your operations in a very efficient manner). However, incase of a tripping of the captive power plant itself, the job of transferring all the load to the grid without affecting the downstream process is not trivial - because the two systems are asynchronous. In that case, we have worked on a concept called islanded bus transfer, i.e. transfer between asynchronous sources.. using an in-phase transfer method.Pl. see www.aartechsolonics.com
Amit.

I was involved in the distant past with a similar scheme for a paper & timber mill and the scheme operations required were extensive and not merely a relay setting.

In the solving of the paper & timber plant problem an extensive "Negative Phase Sequence" protection, monitoring, breaker trip & reclose scheme was installed to prevent the user's generating plant feeding the Grid.

Talk to the relay people they might have "NPS" feature in the specific relays you mention or a "NPS" relay.

Most electricity supply regulations prohibit a degree of energy feedback from a consumer onto the grid & you would also be well advised to talk to them to ascertain what is allowed.

Woodward makes suitable relays/controllers,with these relays and proper coordination system we can achieve your requirement.

Dear Sir,

we already have Woodward MRP2 reverse power relay installed on our grid incomers. But due to some conditions whenever we take out its fuse and deactivate it. We become prone to grid side faults. Our REL 511 does not send any trip command in case undervoltage occurs on grid lines due to some fault.

The problem is also that, whenever any undervoltage occurs on grid, (when connected with our power plant) , our plant is usually isolated by activation of reverse power relay(MRP2) on grid incomers, rather than distance prot terminal REL 511.

Because distance prot should be our primary prot, we want REL 511 to operate for clearing the faults that happens on grid side.

and we want MRP2 relay for power flow monitoring only i.e putting grid in floating condition.

Thanks

thank you so much all for your response ..

The problem is also that, whenever any undervoltage occurs on grid, (when connected with our power plant) , our plant is usually isolated by activation of reverse power relay on grid incomers rather than distance prot terminal REL 511.

Because distance prot should be our primary prot, we want REL 511 to operate for clearing the faults that happens on grid side.

in case anybody needs settings of REL 511 in our plant. i can email you the excel file.

Thanks again.

Nothing will allow your plant to be completely unaffected. The relays and the circuit breakers require a finite amount of time to operate. Until the incomer breakers are open, your generators will supply the fault. You can, however, minimize the effect with a proper protection scheme.

The distance relay is primary protection only for a fault within its zone of protection. If the utility source simply quits, REL 511 has no cause to trip. In this event, the reverse power relay becomes the primary protection. It is likely that the distance relay is not operating because either:

1. the fault is outside your relay's zone of protection, or
2. the utility's relay protection is much faster than your distance relay.

In either case, your distance relay is not seeing a fault of sufficient magnitude and duration to cause a trip. Once the utility supply to your incomer trips, your generators try to supply the external load still connected to the incomer. This causes the reverse power relay to activate a trip. To verify this, you could ask the utility for the cause of the outage and the location of the fault. Compare the actual line distance to the zone defined in REL 511.

Since you can't control or modify the utility's equipment, the best you can do is to ensure that your protection is properly coordinated and functioning. The timing of the distance relay must be faster than the generator protection and the reverse power relays, and the distance relays must be properly set for the size, length and impedance of the incomers.

Thanks so much all for your valuable comments. :)

I will utilise this info and will come back in case i need some more help.

Thanks again.

IT IS BETTER FOR YOU TO GO FOR THE VECTOR SURGE RELAY.

Dear Mr.,

Your problem is a common problem to all the Generating Stations synchronized with Grid.

Your generator feeding Grid Faults & isolation of Grid depends on so many factor. Some are

1) Distance of fault from your Generator

2) Inertia of your Turbine

3) Grid Isolation at Grid side & isolation breaker position from your Generator.

However you must use an islanding relay having the following protections in one relay. The relay shall be fed with voltage & current at incoming to your plant from Grid

1) Voltage vector shift relay, which is also known as Voltage Surge Relay with minimum threshold voltage

2) dF/dt

3) Directional over current towards Grid with voltage control

4) Under Frequency

5) Over Frequency

6) Under voltage

7) Over Voltage

You should avoid using Reverse Power relay to protect your Generator from Grid Fault. This is a displacement relay, not a speed relay.

For details regarding prtection, relay choice, set point etc. feel free to contact me.

Regards.

B K MOHANTY

GM-E&A

Adhunik Metaliks Ltd.

Mob.: 09178454413