Generator Synchronization and Load Control with Mains

Load 4000A will be shared between the two sources as per the source impedence

The generator synchronised with the mains will share power to its max. capacity proportionately. In the event of mains failure, dg switching to run predetermined essential loads, will be on while other loads switch off by giving trip sgnal on mains failure . This can be done with simple aux. relay circuits. When the mains are restored , an auto sync relay cantake up syncronising mains again or after manual snchronising, switch on loads

We have 1250 KVA DG set. And we test it weekly by synchronizing the genset to the system. After that by speed decrease command pulse, we load the genset up to 0.8 to 1 MW load. After monitoring all parameter, reduce the load by giving speed increase command and de-synchronize from the system. You can do it same way. This is without disturbing actual load.

Dear Rajen,

Thanks for your reply,it seems you have also done the similar way but i have one confusion as i understand the generator will take more load if we will increase the speed/frequency by speed potentiometer and to unload we have to decrease the speed/frequency by speed potentiometer but what you have written is just opposite.

Please correct if i have some wrong understanding.

Dear Le Noble,

Thanks for your reply, i will use reverse power relay for preventing generator running as a motor but how can i protect it from overloading? The governor is of Volvo penta ESD5500E which is already having droop contacts i guess i have to close these contacts during parallel run and operator will take care of loading and unloading by speed potentiometer.

Is it really required to control the AVR also?

Kindly advice.

you can use current relay or, I guess your Volvo should be equipped with overload protection, yes it is recommended to watch the KVAr, you may burn the exciter if you run with negative KVAR, you have to control the AVR as well

Hello everybody!

"arif777", your question about AVR control is very important. Things are coming complicated if once a generator is synchronized. Voltage control changes to powerfactor control and speed (frequency) control changes to power control.

First of all, make sure that your mains frequency is stable. Not a problem within Europe and US.

Examples are given for 50Hz, for 60Hz just change it proportional.

Secondly you need to set your AVR to droop as well. Assuming you may have a SDMO set and therefore a Leroy Somer alternator, check the AVR. It must be R 438 or R 448, never R230. Then you will need a current transformer attached to it. Troop setting to be observed.

Background: In modern days, AVR's are very precise, 1% or even 0.5%, which means in return, that a small deviation on the line voltage will cause a huge change to the exiter output. As mentioned before, your alternator will either take reactive power or try to push up mains voltage to "his" preset voltage and supplying reactive power to the grid. Both situations are dangerous and will destroy the windings.

The droop will reduce AVR voltage settings if much reactive power is sent and increase voltage settings if to much is taken. To set the droop:

Idle Generator and adjust voltage. Apply some load and check if voltage goes down. if voltage is rising, reverse the current transformer. Adjust with droop potentiometer.

Example: 5% droop wanted, = 20V at 400V at full load. If you have only 30% load, adjust to 30% of this 20V.

The droop settings on the 5500E controller are easy. Start engine at no load and adjust 50Hz. Assuming 5% droop: Activate droop and set droop setting potentiometer to 52.5Hz. That's all! Engine will come back to 50Hz at full load.

One more thing:

Do you like to overhaul engines, or orange red glowing exhaust manifolds? If not, take care of the power you apply for parallel operation. Here one example for the 16L Volvo engine which was used in 500kVA sets. Rating is 500kVA PRP. This is not engine manufacturer related and applies to all makes.

The real load possible is less than 280kW CON(this may be slightly different for other manufacturers) out of the 400kW PRP. 250kW or less is more advisable. My formula: KVA divided by 2 equals the kW which can be taken for CON demand (example: feed the mains).

Automatic controller is like life insurance, gives you very less trouble. Reverse Power control, protection relays, everything included. Auto mains failure control as well, if wanted with synchronisation back to the mains and non interrupted supply.

All mentioned controllers are ok, the easygen 3000 may be a bargain as prices have been quitly reduced in April. The functions of Package P2 is now included in the standard version. Price stays the same, bargain 200 to 300 $. In opposite to DSE 7510, the easygen 3000 (front panel version is called 3200) can control 2 breakers, mains and generator, the 7510 only the generator breaker.

I do not know the instrumentation of your Generating Set, if there is Powerfactor and Power Display. Both is prerequisite, if you synchronize to mains. Both included in the mentioned Controllers.

By the way, do you pay for demand (max kW usage)? Do you have short power peaks? If yes, set your generator for peak shaving! If demand is higher than average (you name it, what is average) generator will fill in automatic. Easygen can do it off the box.

Anyhow, the post was started, how to synchronize.

Let me come back to one point of "Le Noble". Positive Power.

To make it clear, must read positive frequency.This is the one to set, to receive positive power when the breaker is closed. By the way: How do you want to synchronize? 3 bulbs is the most simple way. Circle with 3 bulbs (500V or 2 x230V in series), the top is L'1-L1, the 2 bottom one L'2-L3 and L3'-L2. L' = Generator L = mains. Positive frequency means, that you run your genset at 51 Hz when mains is 50Hz. The result should be a rotating light sequence. Note the direction , it should go anticlockwise, otherwise reverse L' and L connections. Why reverse? To show you, that you have to reduce frequency. You will find it quite logical, if your speed potentiometer will increase the speed clockwise. At 50 and 51 Hz the light will rotate 1 time per second. Reduce speed to 1 rotation in 5 to 10 seconds. If the top light (L'1-L1) is off AND both bottom lights have same brightness, switch must be closed. You should have positive power now. Did not mention that you have to align generator voltage to the mains voltage. Now increase speed (frequency) potentiometer slightly and adjust voltage potentiometer to powerfactor 1. If the indication is capacitive (Lead), lower the voltage, if inductive (Lag), increase the voltage.

Good luck!

Norbert

The first thing that is surprising about this post is the lack of reference to the original equipment manufacturer's [OEM] operation and maintenance manual [O&M]. The procedure for doing what is wanted will certainly be written within it.

If the O&M is not to hand then a simple telephone call to the OEM will surely invoke the arrival of a replacement.

The second thing that is surprising is the lack of reference to a procedure at the facility that already describes how to do what is required.

The third thing that is surprising is the lack of reference to any training that is provided at the facility to enable others to do what is in the procedure.

What a way to run a facility with a <... 350KVA generator...for supplying critical loads in case of mains failure...>!