So, it is new and never worked before. So we don't know if it is wired right, or programmed right, or even if the control equipment is the right model for the application. No problem we'll pick it off a piece at a time.
Curiousity question: Can these generators run parallel with a utility or other generators?
Here's what we do know:
The generators are phased correctly.
The PTs and sync circuits are phased correctly.
Each generator and associated control equipment operates correctly when running stand alone. (is this true?)
My suggestions are likely things already completed as part of the preliminary commissioning - if so, please verify they were completed.
Do a point to point wiring check for every control wire - every one, cabinet internal, cabinet to generator and auxillary equipment. The best method I have found to do this is to pick a couple of your best techs, get them copies of the schematics/interconnects and a highlighter pen. As they verify each wire, trace it on the schematic/interconnect with the highlighter. If the techs say they have done this, ask to see the "blue-lines". They should be able to show you the interconnect drawings they used and highlighted.
The people that wired it likely used the interconnect diagram. For troubleshooting, you are using the schematic. Verify the interconnect diagram is the same connections as the schematic. Amazingly, sometimes engineering/drafting departments screw things up.
Check the control equipment operating modes programming. There are likely several. Here is an example of a of how it could be:
Islanded - The one on-line gen is in isoc, freq and voltage set by its controller, as set from the raise/lower switches
Paralleling - on-line gen in isoc, off-line gen in droop. Sync control switch in Auto. Off-line gen controller automatically adjusts voltage/frequency until it matches the bus, then issues a CB close command
Paralleled - As soon as the paralleling CB closes, both go to droop, freq and voltage set by a master controller, as set by internal setpoints (individual raise/lower knobs usually are programmed to not be operational), load and var share lines are operating.
You will have to go through the programming and understand exactly which modes are operational.
When we start T/G 2 and synchronize it with T/G1 , T/G 2 absorbs all the load , load on T/G 1 decreases until C.B. trips reverse power.
Selector switches of raising and lowering speed are not functioning during this time.
That sounds like they are both in isoc, using internal setpoints. The load share lines are either swapped or not connected. Or the controller is not programmed correctly for load share.
When speed raising and lowering worked on the Mark VI controller , both turbines kept throwing loads on each others , it never reached steady state.
This sounds like you have a switch that changes between internal setpoints (raise/lower switches don't work) and a manual position that allow the raise/lower switches to be operational. This one is more difficult to understand without seeing the schematics/programming.
Could be programmed for one in droop, and one in isoc. Maybe the droop machine needs to have a little steeper slope.
Could be programmed for one in baseload, the other in isoc. Maybe the controller output to the governors is too fast. TGs generally don't react very quickly to changing loads. Some tend to overshoot then undershoot and may never settle out if the control signal is moving too quickly.
The real problem:
You have a $40 million installation, and it is not meeting spec. You are dealing with a generator mfg, an engineering firm, installation contractor, maybe an assembler for the control equipment cabinet, and a commissioning/FCO crew. Everybody is running scared - nobody wants this to be their fault. The most important troubleshooting skill is getting everyone to talk to you. These people don't really care if the units meet spec or not, they just want their money. It isn't that they are bad sorts, they just have different goals than you do. Their goal is to maximize their income with minimum output. Your goal is to have an installation that at a minimum meets spec, and even better yet meets the customer's needs.
As you learn more, let us know - it is interesting.
Another curiosity question: MarkVI is not enough to identify it. Who is the mfg?
just thought of another: depending of the programming, the symptoms could also be a reversed CT in the load share circuit.
cf
