1. Are you using the right CT's and PT's for your application
Are you using the right CT's and PT's for your application? John Levine, P.E. Levine Lectronics and Lectric GE Multilin / Instrument Transformers, Inc.

2. Alternate Title of Presentation
Now I know what I do not know about CT’s and PT’s.
As engineers we do not need to know all the answers just where to get them.

3. Current & Voltage Transformer Basics (IEEE Standards)

4. Agenda Current Transformers Voltage Transformers
Required Information for Specifying CTs & VTs
Take Home Rules” for CTs & VTs
Applications where used

5. Why use Instrument Transformers?
Circuit Isolation
Reduce voltage and currents to reasonable working levels.
Phasor combinations for summing and measuring power

6. TYPES OF C.T. CONSTRUCTION
CURRENT TRANSFORMERS
TYPES OF C.T. CONSTRUCTION
The most common type of C.T. construction is the “DOUGHNUT” type. It is constructed of an iron toroid, which forms the core of the transformer, and is wound with secondary turns.
Secondary Winding
Primary Conductor
Iron Core
The `doughnut' fits over the primary conductor, which constitutes one primary turn. If the toroid is wound with 240 secondary turns, then the ratio of the C.T. is 240 : 1 or 1200 : 5A
The continuous rating of the secondary winding is normally 5 AMPS in North America, and 1 AMP or 0.5 AMP in many other parts of the world.
This type of `doughnut' C.T. is most commonly used in circuit breakers and transformers. The C.T. fits into the bushing `turret', and the porcelain bushing fits through the centre of the `doughnut'. Up to four C.T.'s of this type can be installed around each bushing of an oil circuit breaker. This arrangement is shown in the following diagram.

7. _____________________
Transformer ratio (TR)
Primary Current
Secondary Current
Transformer Ratio =
_____________________
Primary Current
(100 amps)
Secondary Current
(5 amps)
100 5
___
= 100:5 or 20:1

8. Polarity Remember: Primary current into “polarity” =
Direction of
Secondary Current
Direction of
Primary Current
Secondary
Polarity
Marks
IEEE X1 S1
IEC
Primary
Polarity
Marks
IEEE H1
IEC P1
Remember:
Primary current into “polarity” =
Secondary current out of “polarity”

9. Polarity Remember: Primary current into “non-polarity” =
Direction of
Secondary Current
Secondary
Polarity
Marks
IEEE X1 S1
IEC
Primary
Polarity
Marks
IEEE H1
IEC P1
Direction of
Primary Current
Remember:
Primary current into “non-polarity” =
Secondary current out of “non-polarity”

10. Generator typical wiring

11. What is your application?
If your application is metering , how high do I need to go in current? 2 times ?
If your application is protective relaying, how high do I need to go in current? 20 times ? 40 times ?
400 amps times 20 = 8,000 amps, 400 amps times 40 = 16,000 amps

12. CT Rating Factor (RF) -- IEEE
Rated current x (RF) =
Maximum continuous current carrying capability:
Without exceeding temperature limits
Without loss of published accuracy class
Typical rating factors for Metering CTs are:
1.0, 1.33, 1.5, 2.0, 3.0, 4.0

13. CT Rating Factor (RF) -- IEEE
IEEE C57.13 Accuracy
BX.X RF 4.0
0.60
0.6% Accuracy
Region
0.30
0.3% Accuracy
Region
Accuracy Class - %
10%
100%
200%
300%
400%
0.30
If I want better accuracy, I could use a 25 to 5 CT instead of a 50 to 5 CT and let it operate between 100% and 200% if I do not exceed the rating factor.
0.60
1.0
2.0
3.0
4.0
Rating Factor

14. Short-Time Thermal Current Rating
One (1) – second thermal rating
Expressed as value of RMS primary current
Main influencing factor:
CT primary & secondary wire size
Can be converted to thermal rating for any
time period (t) up to five (5) seconds:
(New RF at new Ambient/Stated RF at 30 degrees C)2=
85-New Ambient/New Ambient
Example: CT with rating factor of 4 at 30 degrees = rating factor of 2.95 at 55 degrees
X2/42=85-55/55 X=2.95

15. Difference in % is known as the “Accuracy”
CT Metering Accuracy =
Actual secondary
current
Rated secondary
current
Difference in % is known as the “Accuracy”
of the CT

16. IEEE CT Metering Accuracy
Class ( * )
Application
High Accuracy Metering
0.15S “Special” High Accuracy Metering
Revenue Metering
Indicating Instruments
Indicating Instruments
* All accuracy classes defined by IEEE C57.13 or C
* Accuracy classes include both ratio & phase angle error

17. IEEE CT Metering Accuracy
Burden
Load connected to CT secondary
Includes devices & connecting leads
Expressed in ohms
Standard values = B0.1, B0.2, B0.5, B0.9, B1.8
E0.04, E0.2
All burdens defined by IEEE C57.13 or C for 60 Hz only

18. IEEE CT Metering Accuracy
Standard IEEE CT Burdens (5 Amp) (Per IEEE Std. C & C )
E0.2
E0.04
0.2
0.04 5 1
1.0

19. CT CLASSIFICATION for Metering
A current transformer for metering purposes may typically have an accuracy of 0.3%. The C.T. must maintain this accuracy for normal load currents, provided the rated burden on the C.T. is not exceeded. It is quite acceptable, and in fact desirable, for the C.T. to saturate when fault current flows. The accuracy for a typical metering C.T. is specified as:
0.3 M 0.9
O.3% METERING O.9 OHMS BURDEN
This metering C.T. has an accuracy of 0.3% when the connected burden does not exceed 0.9 OHMS.

20. IEEE CT Metering Accuracy
“Accuracy” expressed as:
Typical
Examples + =
Accuracy Class
(0.3, 0.6, 1.2) (*)
Burden (Ohms)
(B0.1, B0.2, B0.5, B0.9, B1.8)
0.3B0.2
0.6B0.9
1.2B1.8
0.15E0.2
(0.15*, 0.15S^)
E0.2, E0.04)
* Accuracy class is stated at 100% rated current
* At 10% rated current, twice the error is allowed (5% for 0.15 class)
^ Accuracy class is stated at 100% to 5% rated current

21. IEEE CT Metering Accuracy
IEEE C57.13 Accuracy
BX.X; RF 4.0
0.60
0.6% AccuracyRegion
0.30
0.3% Accuracy
Region
Accuracy Class - %
10%
100%
200%
300%
400%
0.30
If I want better accuracy, I could use a 25 to 5 CT instead of a 50 to 5 CT and let it operate between 100% and 200% if I do not exceed the rating factor.
No accuracy guaranteed at current levels less than 10%
0.60
1.0
2.0
3.0
4.0
Rating Factor

22. IEEE CT Metering Accuracy
CT Parallelogram – IEEE C57.13
0.3 class
parallelogram
10%
100%
0.6 class
parallelogram
Note:
Burden must
be specified
Horizontal line shows the phase angle.
Out of 0.3% Class

23. IEEE CT Metering Accuracy
CT Parallelogram – IEEE C57.13
0.3 class
parallelogram
10%
100%
0.6 class
parallelogram
Note:
Burden must
be specified
Horizontal line shows the phase angle.
Corrected to 0.3% Class

24. IEEE CT Metering Accuracy
IEEE C Accuracy
E0.04, E0.20; BX.X; RF4.0
0.60
0.30
0.15% Accuracy
Region
0.15
0.3% AccuracyRegion
Accuracy Class - % 5%
100%
200%
300%
400%
0.15
0.30
No accuracy guaranteed
at current levels less than 5%
0.60
1.0
2.0
3.0
4.0
Rating Factor

25. IEEE CT Metering Accuracy
IEEE C Accuracy
E0.04, E0.20; BX.X, RF4.0
0.60
0.30
0.15% Accuracy
Region
0.15
Accuracy Class - % 5%
100%
200%
300%
400%
0.15
0.30
S means stepless
No accuracy guaranteed
at current levels less than 5%
0.60
1.0
2.0
3.0
4.0
Rating Factor

26. Standard Relay Accuracy Classes
IEEE CT Relay Accuracy
Protection CT
Standard Relay Accuracy Classes
C or T100
C or T200
C or T400
C or T800
What do these mean?

27. IEEE CT Relay Accuracy
Relay class (C or T___ ) designates minimum secondary terminal volts…
At 20 times rated current
Without exceeding 10% ratio error
Into a maximum specified burden
Now that everyone is totally confused
let’s look at some simple examples …

28. CT CLASSIFICATION for RELAYING
Protection Class CT’s - Must supply 20 times rated current
10 C 400
Format
Accuracy
Voltage at 20 times CT
Letter
CT Classification for relaying
Over the years many standards for CT classification have been developed in North America and Europe. Protection class CT’s are assumed to be able to supply 20 times its rated secondary current to the relay. That means for a 5 amp rated secondary the CT must be able to supply 100 Amps of current, and for a 1 amp rated secondary the CT must be able to supply 20 Amps of current.
The operating principals of CT’s are specified in a format such as this.
The first number represents the maximum amount of error, listed in as a percentage, that this CT will produce. Therefore, the 10 in our example stands for no more then 10 percent error.
The second item, which is always a letter, can either be a T, C, K, L, or H.
If the letter is a T which stands for “test”, it means that the CT accuracy can only be determined by testing the CT. Current transformers with non-distributed windings fit in this category.
If the letter is a C or a K which stands for “Calculated”, it means the CT accuracy can be determined by performing calculation using given excitation characteristics. CTs with fully distributed windings, (bushing CT’s for instance) fit in this category.
If the letter is an L, this indicates that the CT has a “Low internal secondary impedance,”
If the letter is an H, this indicates that the CT has a “high internal secondary impedance,”
T = Determined by test
C = Calculated
K = Calculated
L = Low internal secondary impedance
H = High internal secondary impedance

29. IEEE CT Relay Accuracy C or T100 example Secondary current
100 amps (20 x 5) X1 X2
Burden of
Devices ()
Primary current
24,000 amps
(20 x 1200)
Total Ext
Burden
1.0 
Terminal Volts = 100 CT
1200:5
C or T100
Burden of
Leads ()
Terminal Volts = (20 times rated) (Total external burden)
100 Volts = (100 amps) (1.0  )

30. IEEE CT Relay Accuracy C or T200 example Secondary current
100 amps (20 x 5) X1 X2
Burden of
Devices ()
Primary current
24,000 amps
(20 x 1200)
Total Ext
Burden
2.0 
Terminal Volts = 200 CT
1200:5
C or T200
Burden of
Leads ()
Terminal volts = (20 times rated) (Total external burden)
200 Volts = (100 amps) (2.0  )

31. IEEE CT Relay Accuracy
Standard IEEE CT Burdens (5 Amp) (Per IEEE Std. C )

32. IEEE CT Relay Accuracy Excitation curve includes
voltage required to overcome
internal resistance (DCR) of CT.
Approximately 32 volts.
10% ratio error = (20 x 5) (10%)
= (100) (0.10)
= 10 amps
This Ct is not a C200. Since you can only produce 209 volts, when you take the 32 volts from internal resistance you only have 177 Volts so you can only rate it at C100
How many terminal volts
would you estimate
this CT can produce?

33. With 10% error, IB is anywhere from 4.5 to 5.5 amps
1000:5 CT
IB >4.5 amps
1000 Amps
5amps
IE<0.5amps
With 10% error, IB is anywhere from 4.5 to 5.5 amps
Most Protection CT’s also have a Metering CT accuracy so you could use this value for calculating the error at lower currents

34. CT Burden Calculation How do we calculate this? Secondary currentX1 X2
Primary Current
Burden of
Devices ()
Total
Burden ZT CT
Burden of
Leads ()

35. CT Burden Calculation ZT = RCT + RL + ZB
ZT = Total burden in ohms (vector summation of
resistance and inductance components)
RCT = CT secondary resistance in deg C (DCR)
RL = Resistance of leads in ohms (Total loop distance)
ZB = Device impedance in ohms
Assumption: 3 phase CTs are “Y” connected

36. GE Multilin Electronic Relay Burden
VA = VI. V= IR, So 0.2 = I*I*R.
.2/25 = .008 ohms

37. 100:5 C.T. Secondary Winding Resistance (DCR) = .062 ohm
Resistance of Cable from C.T. to Relay and back = .1 ohms
Resistance of Relay Coil = .02 ohms
Total Resistance = .182 ohms
.062
.02 .1
If we have a fault of 2,000 amps and the C.T. ratio is 100:5 then the C.T. secondary current is 100 amps. Therefore we will produce a voltage of 100 amps x .182 ohms = 18.2 Volts. To prevent CT saturation, select a CT with a knee point above 18.2 Volts.
In this example the resistance of the C.T. secondary circuit, or C.T. burden is:
C.T. Secondary Winding Resistance = 1 OHM
Resistance of Cable from C.T. to Relay = 2 OHMS
Resistance of Relay Coil = 2 OHMS
Total Resistance of C.T. Secondary Circuit = 5 OHMS
If the fault current is 12,000 Amps, and the C.T. ratio is 1200 : 5A, then the C.T. secondary current is 50 Amps. At this secondary current and the above C.T. burden of 5 OHMS, the C.T. must produce a terminal voltage of 250 volts. For the C.T. to operate with good accuracy, without saturating for the maximum fault current, the knee point must be well above 250 volts.

38. 1000:5 C.T. Secondary Winding Resistance (DCR) = .32 ohm
is a 1000 to 5 CT, Class C100
1000:5 C.T. Secondary Winding Resistance (DCR) = .32 ohm
Resistance of Cable from C.T. to Relay and back = .1 ohms
Resistance of Relay Coil = .008 ohms
Total Resistance = .428 ohms
.32
.008 .1
If we have a fault of 20,000 amps and the C.T. ratio is 1000:5 then the C.T. secondary current is 100 amps. Therefore we will produce a voltage of 100 amps x .428 ohms = 42.8 Volts. To prevent CT saturation, select a CT with a knee point above 42.8 Volts.
What happens if the fault current is 40,000 amps?
Here is another exampe with very high resistance in the circuit.
In this example the resistance of the C.T. secondary circuit, or C.T. burden is:
C.T. Secondary Winding Resistance = 1 OHM
Resistance of Cable from C.T. to Relay = 2 OHMS
Resistance of Relay Coil = 2 OHMS
Total Resistance of C.T. Secondary Circuit = 5 OHMS
If the fault current is 12,000 Amps, and the C.T. ratio is 1200 : 5A, then the C.T. secondary current is 50 Amps. At this secondary current and the above C.T. burden of 5 OHMS, the C.T. must produce a terminal voltage of 250 volts. For the C.T. to operate with good accuracy, without saturating for the maximum fault current, the knee point must be well above 250 volts.

39. Factors Influencing CT Accuracy
Frequency
“Low frequency” and “High accuracy” are not friends!!
Current Ratio
“Low ratio” and “high accuracy” are not friends!!
Burden
“High burden” and “High Accuracy” are not friends!!

40. CT Saturation
What is CT Saturation?

41. Power Systems Relay Committee (PSRC) Saturation Calculator
Note in the first cycle the secondary current does not saturate as quickly as in the second cycle. This is called time to saturate.

42. Factors Affecting Degree of Saturation and Time to Saturation
DC Offset
Fault Magnitude (symmetrical current)
100 to 5 times= 2000 amps, at 20,000 amps we have 200 times CT
CT Turns Ratio
Secondary Burden
CT Accuracy
Remanence Flux
Can occur if current interrupted when core is saturated
If DC flows in windings during testing
Need a voltage above 60% of knee point to reduce the remanence to less than 10% of saturation flux density.

43. Tips for Avoiding CT Saturation
Use higher ratio CTs
Use separate set of high ratio CTs for high fault current tripping
Reduce secondary burden
Select low burden relays & meters
Distribute single phase burdens among phases
Increase size of secondary leads
Reduce length of secondary leads
Use “step down” auxiliary CTs

44. Potential Transformers

45. Definitions Voltage Transformer (VT)
An instrument transformer used to reflect a primary voltage into a secondary voltage through a magnetic medium. Always connected in parallel with primary conductor across a circuit load.
Secondary (measuring) voltage is usually 115 or 120 volts nominally. The secondary voltage level is selected for ease of measurement and safety.
Control Power Transformer (CPT)
Designed to provide power for contractors, relays and devices with high inrush currents, Regulation is not as critical.

47. POTENTIAL TRANSFORMERSVP
14,400/120 = 120/1
4200/120 = 35/1
2400/120 = 20/1
Potential Transformers
Potential transformers are used to isolate and step down and accurately reproduce the scaled voltage for the relay.
The primary side of a PT needs to have the System voltage, symbolized as Vp, applied across the input terminals as shown here.
The Secondary side of the PT will then accurately replicates a scaled down version the primary voltage over a defined voltage range . The secondary voltage is symbolized as Vs.
There are two types of potential transformers: Electromagnetic voltage transformer and the capacitive voltage transformers. Vs
Relay

48. IEEE VT Accuracy Class Metering Accuracy Classes (% error) 0.3
0.6
1.2
0.15
Defined by IEEE C57.13
Applicable from 90% to 110%
rated voltage
Defined by IEEE C

49. IEEE VT Accuracy Class Metering Accuracy Class Burdens
These standard burden designations have no significance
at frequencies other than 60 Hz.

50. IEEE VT Accuracy Class Expressed as: Accuracy Class + Burden Code
0.3 W,X,Y
0.6 Z
1.2 ZZ
These standard designations have no significance
at frequencies other than 60 Hz.

52. VT Installation Guidelines
Caution:
Rated voltage: Do not operate above 110%
Line to ground rated:
Do not connect line to line
Do not use on ungrounded systems
w/o consulting factory
Rated Frequency: Do not operate below rated
frequency w/o consulting
factory

53. IEEE VT Groups VT Group No. of Bushing Connection Method
Neutral Grounding
Notes 1 2
open 
Y-Y possible
Any
Withstand 25% over rated voltage on an emergency basis
Withstand 10% over rated voltage continuously. Primary rated for line to line voltage. 3
Y-Y-Y
Outdoor, two secondary windings. Withstand 10% over rated voltage continuously. 4A
Y-Y
Effectively
Withstand 10% over rated voltage continuously & 25% on an emergency basis. For operation at 100% rated voltage. 4B
Y-Broken Corner 
Non-effectively
Withstand 10% overvoltage continuously. For operation at 58% rated voltage. 5
Outdoor. Withstand 40% over rated voltage for 1 minute and 10% over rated voltage continuously

54. VT Typical Connections
Open Delta Connection
(2) Double Bushing VTs
Y – Y Connection
(3) Single Bushing VTs

55. Ferroresonance
Possible with Y connected grounded VTs on ungrounded power systems
A VT is an inductive component
Capacitance to ground exists in the system
When they match ferroresonance may occur
May cause higher VT voltages & saturation
Possible results -- High VT currents
Overheating
VT failure

56. Ferroresonance Recommended reading:
“Ferroresonance of Grounded Potential
Transformers on Ungrounded Power Systems”
AIEE Power Apparatus & Systems,
Aug 1959, pg , by Karlicek and Taylor

57. Ferroresonance Damping
Preferred method
Non effectively
grounded system
Y – Broken Corner  VT connection
Voltage relay to
detect ground
fault
0 normal condition
3 times normal L-N phase
ground fault
Ferroresonance
damping resistor RFR

58. Ferroresonance Damping
Preferred method
Y-Y/Broken Corner  Connection
Double secondary VT
(1) Relaying / Metering
(1) Ground fault detection
and ferroresonance damping

59. Ferroresonance Damping Ferroresonance damping resistor RFR value
Based on 2 variables:
Air core inductance of primary winding (La)
VT ratio (N)
RFR = 100 La / N2
Power rating (watts) of the resistor is a system related problem.
General recommendation is 50% of VA rating of a single VT.

60. for Specifying CTs & VTs
Required Information
for Specifying CTs & VTs

61. Current Transformer (CT) RFQ Specification
Environment: ___Indoor ___Outdoor
System Voltage (kV)
0.6
0.72
3.6
5.0
7.2
8.7 12 15 24 25
34.5
Power Frequency (kV) 4 3 10 19 20 26 28 34 50 40 70
BIL (kV) 10 40 60 75
110
125
150
200
Standard (Check one)
IEEE __
IEC __
IEC __
IEEE __
CT Application: ___Metering ___Protection
Dimensions: ___ Inches ___ mm
Max. Outside: L ______ x W ______ x D ______
CT Window: Round: ______ Diameter; Rectangular: L ______ x W ______ ; Primary Bar: _____
Current Ratio: _______ : 5 _______ : 1
Continued next slide

62. Current Transformer (CT) RFQ Specification (Continued)
Accuracy:
Indication Only: _____ %, _____VA (Skip metering & protection selections)
Metering Class:
IEEE: ___0.3 ___0.6 ___1.2 ___2.4 ________Other
IEC: ___0.2 ___0.5 ___1.0 ________Other
Metering Burden:
IEEE (Ohms): ___B0.1 ___B0.2 ___B0.5 ___B0.9 ___B1.8 ______Other
IEC (VA): ___ ___ ___ ___ ___ ______Other
Protection Class: C______(IEEE) ___VA, ___P___(IEC)
Operating Frequency: ___60HZ ___50HZ
Rating Factor: ___1.0 ___1.33 ___1.5 ___2.0 ______Other
Secondary Connections: ___Terminals ___24 inch leads
Outer Insulation: ___Standard ___Cotton tape & varnish ___Polyester tape
Insulation Class: ___105 0C (Standard) _____Other
Other Special Requirements (dimensional constraints, mounting requirements, …etc):
______________________________________________________________________________

63. Voltage Transformer (VT) RFQ Specification
Environment: ___Indoor ___Outdoor
System Voltage (kV)
0.6
0.72
3.6
5.0
7.2
8.7 12 15 24 25
34.5
Power Frequency (kV) 4 3 10 19 20 26 28 34 50 40 70
BIL (kV) 10 40 60 75
110
125
150
200
Standard (Check one)
IEEE __
IEC __
IEC __
Operating Frequency: ___60HZ ___50HZ
Accuracy:
IEEE: ___W ___X ___M ___Y ___Z ___ZZ ________Other
(Enter 0.3, 0.6, 1.2, or leave blank)
IEC: ___10VA ___25VA ___50VA ___100VA ___200VA ___500VA ______Other
(Enter 0.2, 0.5, 1.0, or leave blank)
Continued next slide

64. Voltage Transformer (VT) RFQ Specification (Continued)
Thermal Rating: _______VA (Optional)
Primary Voltage: ___1 bushing _________VAC - Phase to neutral
___2 bushing _________VAC - Phase to phase
Secondary Voltage: ___120V ___115V ___110V ___100V
___120/3 ___115/3 ___110/3 ___100/3
___Other _________________
Rated Voltage Factor (RVF) (1 bushing only): ___1.9 for 30s ___1.9 for 8 hours ___Other____________
Fuses:
___Primary ___Secondary ___None (600 – 720 V)
___Primary ___Live parts only ___Switchgear Style ___Unfused (2.5kV – 15kV)
Note integral fusing not available above 15kV

65. Take Home Rule # 1 Never open circuit a current
transformer secondary while the primary is energized
CTs are intended to be proportional current devices. Very high voltages can result from open circuiting the secondary circuit of an energized CT. Even very small primary currents can cause damage… Consult the factory if you have questions.

66. Take Home Rule # 2
Never short circuit the secondary of an energized VT
VTs are intended to be used as proportional voltage
devices. Damaging current will result from short
circuiting the secondary circuit of an energized VT.

67. Take Home Rule # 3 Metering applications do not require a “C” class CT
“C” class ratings are specified for protection purposes only. With some exceptions metering class CTs are typically smaller and less expensive.

68. Take Home Rule # 4 CT secondary leads must be added to the CT burden
Electronic relays usually represent very little burden to the CT secondary circuit. In many cases the major burden is caused by the CT secondary leads.

69. Take Home Rule # 5 Never use a 60 Hz rated VT on a 50 Hz System
60 Hz VTs may saturate at lower frequencies and exceed temperature limitations. VT failure is likely…severe equipment damage is possible.

70. Take Home Rule # 6 Exercise caution when connecting grounded VTs
to ungrounded systems
Line to ground voltage on any VT may exceed the primary voltage rating during a fault condition…
VT must be designed for application.

71. Take Home Rule # 7
It is common practice to apply 600 Volt CT to systems with higher voltages.
This practice is done by passing fully insulated conductors through the Window.

72. QUESTIONS?

75. LV Switchboards
LV Panelboards
Typical CT Models
5 Series
19RT
8SHT

76. LV Switchboards LV Panelboards Typical VT Models
460, 467, 475, 2VT460, 3VT460

77. L.V. MCC’s
Typical CT Models
5 Series
19RT
8SHT
3P85

78. L.V. MCC’s
Typical VT Models
460, 467, 475, 2VT460, 3VT460

79. L.V. Switchgear

80. L.V. Switchgear Current Transformers GE 2000 amp frame
Model 560 Metering
Model 561 Protection

81. L.V. Switchgear Current Transformers GE 4000 amp frame
Model 562 Metering
Model 563 Protection

82. L.V. Switchgear No more room in the front?
We can recommend a different model CT for the rear bus area.

83. L.V. Switchgear
Typical 3 Phase VT
Installation
3VTL460
3 Phase VT

84. M.V. Switchgear
Typical Line Up
Where are the CTs, VTs, and CPTs?

85. M.V. Switchgear Current Transformers 778 / 779 680 /780 Series
Typical IEEE Metering & Protection

86. M.V. Switchgear Current Transformers Metering & Protection
Model 780, 778
Model 785

87. M.V. Switchgear
Model 203 CTs mounted in rear bus compartment

88. Is this better than a Residual Connection?
M.V. Switchgear
Zero Sequence CT
Model 593, 594
Is this better than a Residual Connection?

89. M.V. Switchgear Typical VT Rollout Drawer Installed in enclosure
(2) PTG5’s in open delta
configuration
Withdrawn from enclosure

90. M.V. Switchgear Typical CPT Rollout Drawer CPT 5 & 15 kV 5 to 15 kVA
Withdrawn from enclosure
Installed in enclosure

91. MV MCC’s
Let’s open a door
and see what’s
inside

92. MV MCC’s
Typical CT Models
112
115
117

93. Generators
Board Mounted Generator CT

94. Station Class Circuit Breakers
Polyester Taped Bushing CT on
Outdoor Circuit Breaker

95. Station Class Circuit Breakers
Ground Shield
Outdoor BO7 -
Replaces BCT’s in shielded
aluminum housing

96. Power Transformers
Slip over current transformer for installation over exterior of outdoor bushing
Outdoor Type BO7 for Retrofit

97. Power Transformers
Metering applications for indoor instrument transformers
on outdoor power transformers
Air terminal chamber
Indoor PT and Bar type CT

99. Questions?