We have received spurious alarms like 1) GENERATOR COLLECTOR END OVER TEMP 2) GEN COLD GAS COLLECTOR END OVER TEMP 3) GEN FRAME COMMON COLD GAS TEMP 4) GEN STATOR CENTER OVER TEMP 5) GEN COLD GAS TEMP HIGH.

These alarms got reset immediately. Luckily turbine did not initate shutdown.

Can anyone please suggest what could be the reason for these alarms?

 

What have you done to troubleshoot the alarms?

Have you tried checking the terminations at each end of the wiring and all along the length of the wiring?

Are the RTDs three-wire or four-wire devices?

What kinds of interconnecting wire/cable are used to connect the RTDs to the Mk V? Twisted, shielded pairs (two-conductors with drain wires) or twisted, shielded three-wire conductor cables (usually called triads) with drain wires?

Since this is happening to several RTDs, we're most likely looking for something common to these RTDs--like the compensation lead.?.?.?

markvguy

 

Did the temperature readings spike high or trend high?

Greg Ponto
Lead Combustion Turbine Specialist
Elwood Operations
(815) 423-9883 x2232
Email: [email protected]

 

YES, i had checked terminations at each end of these 3 wire RTD.

Interconnecting mk-v cable is twisted pair(not triad) shileded cable. All the RTDs one lag is grounded at the local jb and from there individual wire is taken to mk-v panel for the connection( which means at mk-v end all the three wires are connected for each RTD)

One more incident happened at the same time which was cable fault in our lighting distribution panel.

earthing for the electrical and MK-v system are different. And since this RTDs' one lead is grounded at junction box, what i suspect is that some kind of induced voltage has disturbed the readings of these RTD.

But I am not able to make out that how it happenes inspite of two different grounding system?

One more thought is that grounding for the electrical and instrumention should be connected to plant earth or not. In our case, it is not like that.

please give more insight into this.

 

Ah, the case of electrical ground and instrument ground.... This will most likely always be a perpetual source of contention, argument, confusion, and problems. This author does not wish to wade into that "ditch" any time again; it is potentially a bottomless one and everyone is right and no one is wrong--when they are speaking. Actually, everyone else is wrong no matter who's speaking. Best to let sleeping dogs lie on this one.

GE Speedtronic turbine control systems are NOT intended to be grounded separately from the main electrical plant ground grid.

If you can measure a voltage or potential differential between the plant electrical ground grid and the instrument (or control) ground, then there is some kind of problem--because ground (earth) should be ground (earth), regardless of whether or not it's for an electrical motor or a transformer or a control system. (Again, that's this author's opinion and opinions are like ... well, let's just say everyone has one (an opinion, that is) and to some people they stink.)

markvguy