Automatic Synchronization of Generators using Relays 4

[jhonsom]

1. In the the design of the relay for autosync of generators, what are the different ways to start the autosynchronizer like autostart command?

2. At what frequency and voltage of generator do we switch to autosynchroniser , is it like around 80% speed and 50% voltage?

3. Do we generally raise the speed to around 80% and then give voltage to field of generator to prevent overexcitation?

4. Do we automatically start autosynchronizer when voltage and frequency reaches certain level without manual command or switch?

5. What is the gain of voltage controller and speed governor in the power plant? I mean gain as if I give 1 second pulse what is the change in voltage/frequency?

 

[rhatcher]

My limited experience with autosynchronisers is aboard ships. For the systems I have seen, the operator sets the voltage and speed of the oncoming generator and then turns on the auto-synchroniser. The auto-synchroniser simply controls the breaker closing at the moment f synchronicity. In this case, if the voltage or speed is out of limit, the synchroniser will not close.

I imagine that there may be systems out there that will automatically control the excitation and prime mover speed (instead of a human) to prepare the system for synchronisation before the breaker closing, but I have not seen this.

However, if it is out there, I am sure some of the experienced people in this forum will speak up.

 

[waross]

If the AVR is already set, just turn it on. The Under Frequency Roll Off feature will prevent over excitation. 80%, try closer to 101%

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[rhatcher]

For the type of system I am talking about, the voltage will be set to match the bus and the speed will be set faster than the bus. I am not sure about speed percentages since, as I explained, I am used to manual set-up. I would say that you would want the synchroscope to make less than one revolution per 10 seconds. The slower the better for a smooth transition.

Other than that advice, I will say this. If you are trying to understand an existing system, examination of the schematics will tell you how it operates. If you are buying a new system for installation, again...examination of the schematics will tell you how it operates.

If you are designing a new system from scratch, I would recommend examining existing designs to determine how they operate and picking the design that suits your need.

 

[dpc]

Most generator control systems put the field on around 80% speed. As Bill says, the AVR will bring it up to voltage quickly. Most governors have a output for "near synchronous speed". You can use that to turn on your autosynchronizer. There's no point in turning on the autosynchronizer until the machine is reasonably close to synchronous speed (like 95%).

The autosynchronizer is not an auto-start system - that is done (auto or manual) separately from the autosynchronizer. Also, don't forget to provide a separate synch-check device to supervise the autosynchro, in case it loses it mind.

 

[waross]

I see mostly smaller generators below about 1500 KVA. The AVRs on many sets are left permanently connected. Before UFRO, AVR burnout if the AVR was switched on at low frequencies was common. Now UFRO provides adequate low frequency burnout protection for AVRs.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[catserveng]

Most autosynchronisers have a RUN command input, there are synchronisers that just phase matching and others also do voltage matching.

The most common synchronisre I see is the Woodward SPM-A, Basler also has a good unit but not too common in my area.

Synchroniser should not go active until unit at or near rated speed and voltage or the synchronisre will try to bias the speed and voltage up as the unit accelerates and overshoot.

The dynamic settings of your synchroniser depends on the response of you unit to speed and voltage change requests. Some older synchronisers had limited adjustment for dynamics and required different part numbers for different applications. Newer digital units, like the Woodward SPM-D have broad adjustment range.

Applying an autosynchroniser depends a lot on your plant and operating mode. A standby system wants the engines up fast and closed quickly, and will tolerate a "rough" sync as a trade off for a speedy close. A prime power plant with gas engines or heat recovery may want a long warmup period. I do mostly smaller systems, 100 kW to 5 MW size machines, most of the systems I work on Woodward control based, like the DSLC, EGCP-2 and the new EasyGen controller.

There is a number of ways to do it, a littel more detail about your plant, like prime mover type and size, and application can help get you better answers.

Hope that helps.

Mike L.

 

[jhonsom]

I Thank everyone for your time and effort.

I have a few more questions:
My relay is a digital autosynchronizer with 4 normally open contacts for voltage raise, voltage low to AVR's and frequency raise, frequency low to Govenors. I went through Woodword manual DSLC which controls bias by analog signals. Mine is not analog .

6. This relay is mainly designed to control AVRs and Govenors which are motor controlled with two contacts for Raise and Lower, Can this be extended to other generations of Govenors and AVR's like GE EX2100 exciter contoller, GE MKV controller? What kind of controllers can my relay control?

7. What is the normal slip frequency and voltage difference at which the generators(small, medium and large) is synchronized to the Bus?

8. After successful synchronization (ready to close 52G) , do they close the breaker immediately? or wait for long time for close command? if so how long they wait?

9. I give a range of setting like 0.01 Hz/sec to 5 Hz/sec for Govenors and 0.01 Volts/sec to 10 Volts/sec for AVR to cover wide range of Govenors and AVR's . Pulse ON time setting (corresponds to teeth of the wheel in AVR and Govenor) is 0.1 seconds to 20 seconds. Does this cover every controller?

10. Do all Govenors and AVR have linear characteristics? I mean for each pulse ON time will it respond linearly? I also have a pulse off time for settling down. I just used proportional control, Is this enough?

 

[catserveng]

6. By using an MOP (motor operated potentiometer) yo can use your synchroniser with just about any control that uses a adjust pot for reference.

7. Again varies by application, I try to get voltage match within 2% usually, tighter if a "soft" system. High speed diesels typically use phase match with a short dwell time. Larger engines, especially gas fueld seem to do better with a slow slip rate slightly above rated speed. Woodward has a nice feature that lets you program in the breaker delay time so you can pretty much match the close dynamics to get a minimum "bump" at close.

8. Once the synchroniser gives a close command, breaker should close right away, a sync check relay used with the synchroniser should keep unit from closing out of phase if there is a problem with the auto sync.

9. Not sure, sounds like it should.

10. Do you mean as to their speed or voltage reference setting input? Generally in the equipment I'm familar with the response is fairly linear.

Hope tha helps

 

[jhonsom]

Thanks for all your replies.
Another question:
11. Do we synch the generator at different slip frequency/ voltage difference for different load condition?

 

[dpc]

Load is irrelevant to synchronizing. Generator is synchronized essentially unloaded. Generator output is increased gradually (?) after synchronizing.

 

[Ariganello]

Jhonsom,

Best way to start Auto sync is your run contact on a SPMD or an EasyGen Control. Depends on how many prime movers you have and how you would like to utilize these, I would go with a Easygen. It has low dependent start and stop, you can bias your speed and voltage with the outputs and load share and also utilize the built in ladder logic feature and even extend out with an IKD.

let me know if you need any other info

Phil

Woodward Controls.

 

[jhonsom]

Ariganello,
Does your relay do Autosync for Hydro? Is hydro frequency control linear for Autosync ? Please reply to Autosync for Hydro thread.
Thanks,
Jhonsom