This document discusses the commissioning process and tests for various electrical equipment, including current transformers, voltage transformers, circuit breakers, isolators, switchgear, busbars, cables, and protection relays. It provides checklists of tests and inspections to ensure equipment is properly installed and functioning correctly before being placed into service. These tests help demonstrate equipment was not damaged during transit, is installed correctly, meets specifications, and protections are correctly set based on calculations.

1. 1
Commissioning of Electrical
Equipment/systems
By - Alemayehu Asmare
Mersa ATVET College, 2015 E.C

2. 2
Significance of Commissioning
tests
Type Tests:
• To ensure compliance with the relevant
National and International specifications &
standards
• To ensure that the manufacturer’s
performance claims are met
• To ensure design validation

3. 3
Routine Tests
• To check quality of compounds used in
manufacturing
• To conform that individual protection
equipments have been correctly
manufactured and set up

4. 4
Commissioning Tests:
• To demonstrate that equipment has not been
damaged in transit and that it can be safely
and confidently connected to the system .
• To prove that the specified equipment has
been correctly installed
• To show that the characteristics of the
protections which are based on calculations
are correct
• To provide a set of test figures for future
reference when required

5. 5
CURRENT TRANSFORMERS
COMMISSIONING CHECK LIIST
SYSTEM : ----------- LOCATION---------
MAKE OF CT & Serial NO:
1.0 CT Particulars:
Protection / Metering :
Ratio :
Accuracy & Burden :
Type : Oil filled / bar /wound / cast
Core balance / Current balance:
Any other details :

6. 6
2.0 Visual Inspection:
3.0 Continuity:------ CT Resistance:----
4.0 Megger Test :---- volts -----M.ohms
5.0 High Voltage Tests
6.0 Polarity Check :
7.0 Ratio Test :
8.0 Magnetising Curve:
9.0 Oil Test results for BDV and Tan Delta
tests

7. 7
VOLTAGE TRANSFORMER
SYSTEM:------- LOCATION:---
Make and Serial No:
1.0 PT Data:
Protection / Metering :
Ratio :--- Accuracy:---- Burden:----
Any other specific details:
2.0 Winding Continuity and Resistance:
3.0 Megger Test :
4.0 High voltage test:

8. 8
5.0 Polarity Check:
6.0 Ratio Test :
7.0 Oil test results

9. 9
HT / LT BREAKERS
SYSTEM: ---- LOCATION:---
Make and Serial No:
1.0 Breaker Details:
Breaker type:
Rated Voltage:-- Current:---
Breaking Capacity:

10. 10
Checks on Breakers:
• Whether breaker rack in and out is smooth
• Breaker primary contacts are firm and tight on
bus bar
• Check automatic operation of the shutter
closing mechanism and ensure its effectiveness
for safe shielding
• Check that all the fuse holders,mechanical
position indicators are properly fitted
• Check that all indication meters,lamp holders
are fixed properly

11. 11
• Check that shrouds are provided to prevent entry
of vermin when the breaker is withdrawn outside
• Check that the breaker is tested for high potential.
• Check limit switches are positioned and proper in
multiple operations
• Check breaker Main /Arcing contact alignments
are proper
• Check oil level in all three poles
• Check auxiliary contacts for positive and proper
operation
• Check spring charge mechanism Motor

12. 12
• Check spring charging mechanism operation
is proper(Both manually and electrically)
• Check closing spring mechanism is in good
condition
• Check breaker close/open indicators are
firmly mounted and they indicate properly
• Check proper functioning of breaker
interlocks for Test / Service position
• Check breaker locking arrangement is
adequate

13. 13
• Check breaker body contacts ,insulators and all
accessories mounted on breaker are thoroughly
observed for any physical damage
• Check interlock between link and breakers
• Check closing and opening operation manually and
mechanically
• Check the operation of the following interlock
mechanisms:
# Breaker cannot be withdrawn or racked in to
service position unless it is in “OFF “ condition
# Panel door can not be opened unless the breaker is
in OFF condition

14. 14
# Panel door cannot be closed with the
breaker in ON condition
# Access flaps for operating the CB and
withdrawing CB can be independently locked
to prevent unauthorized operation.
• Check that panel door can be locked securely
• Check and record the following Values:
 Closing Coil Megger value
 Trip Coil Megger value
 Pick up and drop out values of closing and
opening coils for closing and opening operation

15. 15
 Spring Charging Time:
 Insulation resistance between the following
values: Breaker poles (Breaker open condition) –
Breaker pole to earth Br. Closed condition)
 Breaker Closing Time:
Breaker Opening Time:
Resistance in Closing coil circuit and opening
coil circuit:

16. 16
HT / LT SWITCHGEAR
Checks on BUS BARs:
• All bolted connections on the bus bar are checked
for tightness
• Phase to phase and phase to earth clearances are
adequate at all points
• Bus bars are adequately supported and clamped
• Bus bars are not mechanically stressed
• Megger values are bus bar
• High voltage test

17. 17
Checks on Cubicles:
• All cubicles are properly bolted to each other and
to floor
• All extra opening are closed
• Doors operate freely,with out jerks and close
properly
• All gaskets for enclosures / doors etc are proper and
adequate
• All ventilation covers are unobstructed and clean
• Check tightness of all panel cover bolts and
mounting screws / bolts of PTs / CTs/Relays and
other apparatus

18. 18
• Check TWO distinct earth connections from the
panel to earth mat.
Checks on Control and Protections:
(Relevant drawings are to be made available)
• Check control wires are connected firmly and no
damage done to TBs
• Check the control wiring is neatly dressed,grouped,
glanded, placed in cable channels with ferrules and
easily identifiable without disconnection
• Check relay connections and CT secondary
connections are firm and proper.

19. 19
• Check control fuse ratings are of proper type as per
drawings.
• All blockings provided on relays are removed
• Control cables insulation tested
• Relays and settings with ranges available
Checks on Cables:
• The cables are properly sealed /grounded/connected
and extra openings are closed
• Non magnetic gland plates are provided for single
core cable entries
• No damage done to cable insulation while
removing the sheath

20. 20
• Cable lug crimping is done properly and ensure
that no oxide paste is applied on cable core at the
time of crimping
• Cable are properly clamped to avoid strain on the
connecting bus / insulator
• Bolting holes in their lug suits the bolt
• Cable connection on the bus bars are tight and
corrosion inhibiting compound is applied at
dissimilar metal functions
• Check for single core core cable,the glands and
metal washers used are non magnetic
• HV test & Megger value
• Check for armour earthing

21. 21
Checks on Relays:
Protection:---- Location:----
Relay designation:-----
• Relay Data:
 operating voltage / current:
 Make & Sl.No:
 Type :
 Time delay range: _-----(PU); ----- (DO)
 Settings:
 Range available
• Physical damage if any:
• Whether all blockings are removed
• Wirings are are checked

22. 22
• Operating coil resistance:----
• Resetting coil resistance:----
• Main coil PU: ----- V / A / AC / DC / %
• Main coil DO:---- - do-
• Reset coil PU:--- -do-
• Reset coil DO:--- -do-
• CT ratio tap used:
• PT ratio tap used:
• Max. feeder load:
• Circuit voltage:

23. 23
ISOLATORS
• Checking of Motor Operated Mechanism
box
• Checking of Isolator and earth switch
interlocks
• Checking of alignment of power
contacts,fixed contact assembly and moving
arm assembly.

24. 24
• Check the healthiness of motor
• Check the operation of isolator for close and
open command
• Check the action of limit cut off for open and
close
• Measure the contact resistance of Main
contacts
• Check the isolator over traveling protection
mechanism

25. 25
Questionnaire
1. Write two electrical tests to be conducted
on equipment insulating oil?
2. Which of the following equipment is
called as Instrument Transformers?
3. Identify the test which ids not common for
CT & PT
a. Megger b. Polarity Check
c. Magnetizing curve d. Ratio

26. 26
4. What is MOCB?
5. What is SF6?
6. What is the difference between Isolator
and Breaker regarding usage?
7. Write one of the most important electrical
test on Isolator?
8. If a particular core secondary is not used
while taking into service,what precaution
is to be taken?
9. In any breaker,which operation time will
be higher?

27. 27
10. Mention some of the Operating
Mechanisms of Breaker?
11. Any electrical panel or equipment should
have how many earthing provisions?
12. For any electrical systems,healthiness of
insulation is ensured by which test?
13. Protection relays are operated on which of
the following?
a. Voltage b. Current c.Both
14. Before taking up any work on reenergized
bus/switchgear,what should be done first?