08-18-1976 HUCMSpecial Meeting
August 18, 1976
All Commissioners were present; also Ruth Hakel, Don Schimp,
Counsel Peterson, Ivan Larson, and "Butch" Wentworth of the
Utilities; Thor Bank, Wally Jensen, and Carl Wardlow of
Associated Consultants, and Bill Eslick of E. A. Pederson
Company.
The Meeting was called to order at 2 P.M. by President Quade.
The purpose of the meeting was to open bids for the Construction
of a 69KV line and Substation Modification for the Municipal
Electric Utility.
Two bids were submitted: Harold H. Scholz Company of Ralston,'
Omaha, submitted a bid for $212,900.00 with 240 calendar days
for completion using 20 days for de- energized lines. An alter-
nate called for $232,900.00 using 240 days with 15 days allowed
for de- energizing.
E. A. Pederson Company of Omaha submitted a bid for $216,900.00
using 200 calendar days with 90 days of de- energized lines. No
alternate bid was given.
Associated Consultants were instructed to analize the bids and
recommend the one to be considered as having the best bid.
A letter from Associated Consultants concerning the Storage Tank
that was damaged by a recent wind storm was discussed in detail.
Pittsburgh -Des Moines Steel Company, the supplier, proposes to
re -use some of the damaged material and to repair the tank bottom.
On a motion by Commissioner Filk, seconded by Commissioner Tracy,
and carried, it was stated that Associated Consultants direct
Pittsburgh -Des Moines Steel Company that the Commission will
accept only a new tank.
there being no further business, the meeting adjourned at 3:30 PM.
Clint& acy, Secretary
ATTES
H. P. Quade, President
Special Meeting
August 26, 1976
All Commissioners were present; also Ruth Hakel, Counsel
Peterson, and Don Schimp of the Utilities; also Don Swanson
and Dave Schmidt of Associated Consultants, Inc.
The meeting was called to order by President Quade at 9 A.M.
Upon reconnendation, a motion was made by Commissioner Tracy,
seconded by Commissioner Filk, and carried, to accept the bid
of Harold H. Scholz Company of Ralston Omaha, for $212,900.00
with 240 calendar days for completion using 20 days for de-
energized lines for Construction of a 69KV line and substation
Modification.
Dave Schmidt presented a report on the electrical events causing
the August 14, 1976, shutdown of the G.E. 11Stag" turbine unit.
At 8:00 AM on August 14th, 1976 the City of Hutchinson's
entire (approx. 14MW) electrical load was being supplied
by the G.E. Co. "STAG "unit. The UPA 13.8KV intercon-
nection circuit breaker 'C3xB3' was closed at the time
although there was no power flow through it. At this
time the interconnection breaker was manually tripped
open to permit a scheduled change of the no load tap
changer on the 15/28 MVA interconnection transformer.
This was being done to correct low voltage conditions
on the Hutchinson 13.8KV bus.
Immediately after the 13.8KV interconnection breaker
was opened the 'STAG' unit 13.8KV station power circuit
breaker automatically tripped open. This was due to
the operation of the overcurrent relay in the neutral
of the 500 KVA station power transformer bank. Loss of
station power to the 'STAG' Unit caused the fuel sole-
noid to stop fuel flow to the combustion chamber of the
'STAG' Unit. To the best of our knowledge this solenoid
functioned properly.
The 'STAG' Unit lost speed rapidly as the load remained
connected to its generator. The lights were reported
to have dimmed slowly to blackout conditions in the dis-
patch room. It has not been possible to clearly estab-
lish what eventually caused the 'STAG' unit 13.8KV gener-
ator breaker to operate. However, it appears that the
Speed - tronic underspeed delayed -trip function most likely
caused the generator breaker to trip open automatically
after a few seconds following the loss of station power.
Positive information as to which alarms indicated on the
enunciator panel was not recorded on the plant log sheets.
!l
1
After the unit shutdown, the plant operating personnel
assumed that the turbine had not suffered any damage
and proceeded to restart the unit. It would not restart.
The above is a summary of the occurances as described
to Mr. Wallace Jensen on August 19th by the plant operat-
ing personnel and per the trouble call report dated
August 14, 1976, copy enclosed.
We have carefully reviewed the station power transformer
bank which supplies electric power to the 'STAG' Unit.
This station power transformer bank was found to be
connected grounded Wye primary, 480 volt delta secondary.
This connection causes this transformer bank to become
a "grounding transformer bank" which balances any primary
voltage differences between phases. There are three
transformer locations at the power plant site that serve
to establish a ground potential reference on the neutral
of the Hutchinson 13.8KV grounded Wye system. These are
the Interconnection transformer, Buss tie transformer,
and the 'STAG' Unit station power transformer bank.
With all three transformers connected to the system the
neutral current in the 'STAG' Unit station power bank
is relatively small; however, with the disconnection
of the interconnection transformer there would be a
rise in this neutral current because only,two trans-
former banks are establishing the ground potential
reference. With this rise in neutral current, the neutral
overcurrent relay operated as expected on a grounding
transformer bank neutral.
We recommend that the neutral on the 'STAG' Unit station
power bank be disconnected from ground such that it is
floating similar to the other station power transformer
banks for the other generating units at Hutchinson.
Associated Consultants
Don Schimp presented a report of the repair of damaged parts
of the G.E. "Stag" turbine unit. After discussion a motion
was made by Commissioner Filk, seconded by Commissioner Tracy,
and carried, to repair and replace as per estimate of Page 1
of the report.
SUBJECT: Shutdown of Stag Unit
DATE: August 14, 1976
TIME: 8:00 A.M.
Engine Hours: 30,023 Trips: 337
Two employees and myself on 8 -14 -76 were at the Plant
for the purpose of changing taps on our 69KV transformer.
We had been having a voltage problem and were going to
set up the voltage 1 tap at this time. The Dispatcher
was taking the full load on the Stag Unit to bring our
meter to 0.(point) where we would be taking no power
and putting no power on the grid.
a
At this time, when we opened the breaker number C3XB3
to take the 69KV line out of service, the station 8
power to the Stag Unit automatically tripped. When
this happens.... your turbine shuts itself down auto-
matically. As I was in the Dispatching,.room I noticed
the lights there becoming dimmer and dimmer, and
they finally were out completely. At this time the
Operator was securing the turbine. The Dispatcher
closed the breaker to the 69KV line so we could get
power back to the City of Hutchinson, The power was
out approximately a minute and 45 seconds to two minutes.
After we had the power for the City of Hutch the Operator
started engines 2, 3, 4, 5, and 7 and was picking up
load on the engines so that we could complete our job
on the transformer. We had the load on the engines and
our meter on zero. The Dispatcher opened up the breaker
C3XB3 to open the breaker on the 69KV line. When he
did this the same sequence of events happened: The
station power for the engines stayed on and there was
no problem with the engines at this time.
We changed the taps on the transformer and re- energized.
the Buss and then proceeded to start the turbine back up.
We made a visual check of the turbine—all lube oil
systems were operating as they should, the steam in
the boiler was down to 200 pounds, the water level was
correct in the boiler, there were no enunciator lights
on the panelboard at this time, the READY light was on,
so the Operator went ahead and started the turbine.
The cranking motor brought the turbine up to firing
speed ... all cans fired... and the turbine was slowly
brought up to synchronizing speed, sychronized with some
load on the turbine, opened our control valves to the
steam turbine and proceeded to load the turbine to 5000KW.
At this time the TIME was 9:15 A.M. We were at full load
at 9:40 A.M.
The turbine tripped off at 9:58 we got enunciators Flame -out,
position Servo, vibration, and steam drum. As the turbine
was coming down to a stop a slight vibration was noticed
and at this time I went out and made a visual check of
the turbine and found that on the one bearing on the
accessory gear some paint burned off the housing. I left
orders with Operators that the turbine was not supposed
to be started until we had a chance to check why this
burned spot was there.
I contacted General Electric Company to have a Service
Engineer come out and inspect this bearing on the Acces-
sory gear housing. He arrived on Sunday morning the 15th
at 8 A.M. We had two people here and moved the cover
off the accessory gear box. We proceeded to take the
accessory coupling off and check the thrust bearing on
the rotor on the turbine and found that the rotor had
moved approximately 1 hundred eighty thousandths of an inch.
We then proceeded to dismantle the turbine to see the
extent of damages on the inside. Don Schimp
Production Supt.
L1 S.
n�
Commissioner Filk presented a report on an up -to -date proposal
to be presented to the "Union" representatives on their next
meeting. After discussion the Commission directed Commissioner
Filk and Counsel Peterson to proceed with the presented proposal.
The meeting adjourned at 11:30 A.M.
P1
Clinton Tracy, Secreatry
Special Meeting
September 1, 1976
All Commissioners were present; also Don Schimp, Ruth Hakel,
and Manager Alexander, Orville Kuiken and Bill Marquardt.
President Quade called the meeting to order at 10:30 A.M.
Don Schimp reported on progress of repairing the G.E. Stag Unit.
An upgraded estimate of repair was presented. After discussion
a motion was made by Commissioner Filk, seconded by Commissioner
Tracy, and carried, to proceed with repair of the damage using
new parts where necessary.
Orville Kuiken gave a report on the outlook of gas availability
from Northern Natural and the curtailment program proposed.
After discussion a motion was made by Commissioner Filk,
seconded by Commissioner Tracy, and carried, to rescind the
motion of April 12, 1976, concerning use of gas only for resi-
dential and apartment houses up to 5 units.
A new motion by Commissioner Filk, seconded by Commissioner
Tracy, and carried, to furnish gas to residential and commercial
accounts up to a daily use of 70 MCF per day and that this
continue until our supply is not ample, was then made.
After discussion about the Union contract a motion was made
by Commissioner Filk and seconded by Commissioner Tracy, and
carried, to accept the Proposal as presented.
The meeting adjourned at 11:45 A.M.
inton Tracy, Secretary
1
1
D