PREVENTIVE MAINTAINANCE AT 220/33KV KIDATU
SUBSTATION
REPORT
18th March 2019
Introduction
Preventive maintenance is a routine activity which is conducted
annually for Substation equipment’s to maintain the reliability of power
supply and identify the faulted equipment for repair or replacement
whenever needed.
The Joint preventive maintenance works were carried out at 220/33kV
Kidatu Substation in Morogoro under Transmission Substation team.
Kidatu Substation has the following bays;
 220kV Generator 1
 220kV Generator 2
 220kV Morogoro line one
 220kV Iringa line
 220kV bus coupler
 220kV Generator 3
 220kV Generator 4
 220kV Morogoro line two
 220kV Kihansi line
 220/33kV Transformers T5 and T6
 33kV Switchgears.
Preventive maintenance (PM) works at Kidatu substation involved Visual
inspection, investigation, testing and repair of the 220 and 33kV substation
equipment to ensure all substation equipment functioning according to
international (IEC) standards.
Works carried out
 General cleaning of control cubicle, Tele protection and protection
systems
 Testing of protection relays for 220kV Morogoro 1, Transformer T5 &
T6 and 33kV
 Verification of healthiness of control and protection systems
 Measurement of Earth Resistance and Continuity checkup for all
substation equipment
 Verification and Testing of healthiness of Dc supply systems
 Physical/Visual inspection to observe any abnormalities of the
equipment
 Functional Test for 220kV Circuit Breakers
 Functional Test for Isolators
 Troubleshooting and Repair
 Stop oil leakage for 22.5MVA, 220/33kV Transformer, 220kV Current
Transformer
 Tele-protection systems
Table below shows the works carried out
BAY NAME
EQUIPMENT
220kV
Kidatu-
System
overall
Morogoro
Line 1
PROBLEM
FOUND
Failure
to
close
on
remote
operation
NECESSARY REMARKS
MEASURE
Troubleshootin Completed
g revealed loss
of Dc supply to
one of control
circuit module
hence solved
Failure of the Troubleshootin Completed
voltages on g reveal that
metering
the PT voltage
system
MCB’s
were
tripped
110V
DC Rectified
Completed
earth fault
General
Cleanness on Completed
cleanness
panel
and
switchgears to
remove dusts
and unwanted
materials
Missing
of Rectification by Completed
interconnecti reconnection
ons
of the
missing
earthing
point
system to the
equipment
on
switchyard
Protection
Relay
Tele
protection
Circuit
Breaker
Inadequate
level
of
aggregate at
220kV yard
Main
distance
relay Micom
442
was
switched off
due
to
blocking of
the
HMI
buttons.
Protection
functionality of
the
distance
relay
were
tested and give
the good result
but jamming of
the buttons not
resolved
Main
II
protection relay
tested and give
the good result
Testing of the
backup Over
current
and
earth fault relay
Alarm
on Testing
for
SEL for MG1 communication
with Morogoro
by
injecting
tele-protection
signal on the
protection relay
was
done
successfully
Testing
for
functionality of
the CB by using
CB
analyzer
equipment and
Pending
Pending
waiting for
the
replacement
of the Micom
P442
Completed
Completed
Pending
waiting for
HSF cards in
telecommuni
cation
multiplexer
Completed
22.5MVA,22 Transformer
0/33kV
T5
Transformer
T5
Protection
equipment
Generator
Current
No. 2 bay
transformer
220/33kV
S/S
Switch Yard,
Control and
protection
equipment
and all other
equipment
220kV Iringa Isolators
line
misalignment
33kV
feeders
Testing of the
protection
relay for the
33kV feeder
Oil leakage
on
tap
changer
Oil leakage
on
current
transformer
R-phase
Dirty on the
Current
transformer
R-phase
the result are
good
Tightening and Completed
applied quick
epoxy
on
leaking points
Testing of the Completed
protection relay
Stop leakage Completed
by tightening of
bolts and nuts
Cleanness to Completed
remove
the
stain on the
leakage phase
Measurement
Completed
and verification
of
earthing
resistance and
continuity
of
switchgears for
the
entire
substation.
Pending
Waiting for
shutdown to
analyze and
rectify
the
problem
protection relay Completed
(NR PCS9611)
was tested and
the results are
good
Recommendations
Most of the switchgears equipment (circuit breakers and disconnectors) are
aged. Circuit breakers for MG2, Iringa, Bus coupler, generator No. 3&4 and
Transformers were manufactured in 1980’s. some of the switchgears are
obsolete which challenge on availability of spare parts. We kindly
recommend to consider on budgeting for replacement.
Substation aggregate should be refilled to reduce the substation potential
effects for the personnel.
Conclusion
Due to limited availability of the equipment; Preventive Maintenance works
for 220/33kV Kidatu substation was done successfully for some parts of the
equipment.
Attachment
1. Relay Test results
2. Test result for Circuit breakers
3. Pictures for different event and equipment’s.
List of Participants
Eng. Jaffari Msuya
Eng. Benjamin Kalenga
Eng. Mary Mitimingi
Eng. Mensiah Gabriel
Honorius Ngonyani
Jackson Mwinuka
Elkana Yona
Test result for Circuit breakers
a. Timing test for 220kV Kidatu – Morogoro 1 Circuit Breakers
Circuit Breaker closing
Red
Yellow
Blue
61.1 mS
60.5 mS
69.1 mS
Circuit Breaker opening
Red
Yellow
Blue
27.8 mS
28.2 mS
29.3 mS
b. Timing test for 220kV Machine No.2 (T2) Circuit Breakers
Circuit Breaker closing
Red
Yellow
Blue
60.1 mS
60.6 mS
58.7 mS
Circuit Breaker opening
Red
Yellow
Blue
28.3 mS
28.6 mS
28.9 mS
EVENT PICTURES
Missing and reconnection of Earthing system on structure
Misalignment of 220kV line asotetor for Iringa line
Transformer Tapechange leakage and rectification process
Leakage sports on Current transformer
Rectifications and cleanness