Electrical Design Manager HV Breaker

HV Breaker Calculator

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HV Breaker Specifications

Electrical power transmission networks, power transformers and HV busbars are protected and controlled by High Voltage Circuit Breakers inside electrical grid located in power terminals and substations.

The protection relay schemes for the protection of the breakers, while protecting other equipment and busses from various types of overload or ground faults can be complex.

Electrical protection of HV breakers is discussed in detail in the Reference Notes located on the navagation bar.

Note: The hashtag (#) symbol on a cell title indicates additional information is available, access it by clicking on the hashtag.

Breaker Selection Inputs

Input Type	Input Unit	Output
Breaker Duty (#)
Tank Type (#)
Bus Configuration (#)
Manufacturer (#)
Breaker Volt (#)
Insulation (#)
Trip Coils (#)

Associated Transformer Inputs

Input Type (From Associated Transformer Module)	Input Unit
Transformer ID
Transformer Primary Volts
Transformer Secondary Volts
Transformer Amps (in MVA)
Transformer kW
Transformer Impedance Z%
Transformer Short-Circuit Load (in kA)

Breaker DC Motor Calculator

Input Type	Input Unit	Output
Motor HP
Starting Amps
Running Amps
Operating Range (DC Volts)

Breaker BIL Insulation Level Table

Input Type	Input Unit	BIL
Primary Insulation Level

Breaker Short Circuit Interrupting Selector #

Breaker Short Circuit Interrupting Selection Table
Voltage Class (kV, RMS)	Rating Factor (K)	Current Rating (A, RMS)	Short Circuit Curret (kA, RMS)	Rated Interruption time (ms)	Trip Delay (Y, sec)	Rated Latching Current (kA, Peak)

Breaker Tables

Select Breaker Table

Breaker Short Circuit Table.
Voltage Class (kV, RMS)	Rating Factor (K)	Current Rating (A, RMS)	Short Circuit Current (kA, RMS)	Rated Interrupt Time (ms)	Trip Delay (Y, sec)	Rated Latching Current (kA, Peak)
15.5	1	600/1200	12.5	83	2	33
15.5	1	1200/1200	20	83	2	52
15.5	1	1200/1200	25	83	2	65
15.5	1	1200/2000/3000	40	83	2	104
25.8	1	1200/2000	12	83	2	33
25.8	1	1200/2000	25	83	2	65
38	1	1200/2000	16	83	2	42
38	1	1200/2000	20	83	2	52
38	1	1200/2000	25	83	2	65
38	1	1200/2000	31.5	83	2	82
38	1	1200/2000/3000	40	83	2	104
48.3	1	1200/2000	20	83	2	52
48.3	1	1200/2000	31.5	83	2	82
48.3	1	1200/2000/3000	40	83	2	104
72.5	1	1200/2000	12.5	83	2	52
72.5	1	1200/2000	12.5	83	2	82
72.5	1	1200/2000/3000	12.5	83	2	104
123	1	1200	20	50	2	52
123	1	1600/2000/3000	40	50	2	104
123	1	2000/3000	63	50	1	164
145	1	1200	20	50	1	52
145	1	1600/2000/3000	40	50	1	104
145	1	2000/3000	63	50	1	164
145	1	2000/3000	80	50	1	208
170	1	1200	16	50	1	42
170	1	1600	31.5	50	1	82
170	1	2000	40	50	1	104
170	1	2000	50	50	1	130
170	1	2000	63	50	1	164
245	1	1600/2000/3000	31.5	50	1	82
245	1	2000/3000	40	50	1	104
245	1	2000	50	50	1	130
245	1	2000/3000	63	50	1	164
362	1	2000/3000	40	33	1	104
362	1	2000	63	33	1	164
550	1	20000/3000	40	33	1	104
550	1	2000	63	33	1	164

Altitude Correction Factors Voltage & Currrent
Altitude (ft)	Voltage ACF	Current AFC
3300	1.0	1.0
5000	0.95	0.99
10000	0.8	0.96

Internal Breaker CT Config

The Current Transformer ( C.T. ), is a type of “instrument transformer” that is designed to produce an alternating current in its secondary winding which is proportional to the current being measured in its primary. Current transformers reduce high voltage currents to a much lower value and provide a convenient way of safely monitoring the actual electrical current flowing in an AC transmission line using a standard ammeter. The principal of operation of a basic current transformer is slightly different from that of an ordinary voltage transformer.

There are a variety of metering applications and uses for current transformers such as with wattmeter’s, power factor meters, watt-hour meters, protective relays, or as trip coils in magnetic circuit breakers, or MCB’s.

Current transformers can reduce or “step-down” current levels from thousands of amperes down to a standard output of a known ratio to either 5 Amps or 1 Amp for normal operation. Thus, small and accurate instruments and control devices can be used with CT’s because they are insulated away from any high-voltage power lines.

EDM assumes current transformers have a standard secondary rating of 5 amps with the primary and secondary currents being expressed as a ratio such as 100/5. This means that the primary current is 20 times greater than the secondary current so when 100 amps is flowing in the primary conductor it will result in 5 amps flowing in the secondary winding.

CT Selection

Breaker In

Input Type	Input Unit	Output
Breaker In CT#		none
Max CT Ratio		none

Breaker Out

Input Type	Input Unit	Output
Breaker Out CT#		none
Max CT Ratio		none

Current Transformers Summaries

Breaker In

Information					Connections - Control Building
HVCT# Breaker In		Ratio	Connections	Function	Accuracy	Relay Mfr	Relay Model

Breaker Out

Information					Connections - Control Building
HVCT# Breaker Out		Ratio	Connections	Function	Accuracy	Relay Mfr	Relay Model

Ref #	Designation	Breaker Device
1	63GA1	Low Gas Pressure Alarm (#)
3	63GL1	Low Gas Lockout Alarm
5	49MX1	Spring Charge Fail Alarm
7	30TH1	Tank Heater Fail Alarm
9	43L/R1	Breaker Control In Local

Ref #	Designation	Breaker Device
1	63GA1	Low Oil Alarm
3	63GL1	Low Gas Lockout Alarm
5	49MX1	Spring Charge Fail Alarm
7	30TH1	Tank Heater Fail Alarm
9	43L/R1	Breaker Control In Local

Ref #	Designation	Breaker Device	Selection
1	43-1	Trip/Close
2	43-2	Local/Remote

Breaker Cable/Bus Design

Copper and aluminum are the two major conductor materials used for substation buses and equipment connections. Both materials can be fabricated into various types of flexible or rigid conductors. The trend in substation construction is toward use of mostly aluminum conductors. Copper conductors are used principally for expansion of similar systems in existing substations.

The conductivity of aluminum is from 50 to 60 percent that of copper, depending on the aluminum alloy. Consequently, larger aluminum conductors are required to carry the same currents as copper conductors. The larger aluminum conductor diameters result in greater wind and ice loads but tend to minimize corona, which is more of a problem at higher voltages.

For the same ampacity, copper conductors weigh approximately twice as much as aluminum conductors. The higher copper conductor weights can result in more sag as compared with aluminum conductors for equal spans. To reduce the sag, it is usually necessary to increase the number of supports for rigid conductors or, in the case of flexible conductors, increase the tensions.

Aluminum conductors are available in a variety of alloys and tempers with different conductor conductivities and strengths. Round tubular conductors are usually specified as either 6061-T6 or 6063-T6 alloy. The 6063-T6 alloy has a conductivity approximately 23 percent higher and a minimum yield strength approximately 29 percent lower than the 6061-T6 alloy. Consequently, the 6063-T6 alloy can carry higher currents but may require shorter support intervals. Both Schedule 40 and 80 pipe are available in either alloy. The Schedule 80 sizes have wall thicknesses approximately 40 percent thicker than the Schedule 40 sizes, resulting in lower deflections for equal span lengths.

T6101-T6 is an aluminum round tube containing a heat treatable wrought alloy best suited for applications involving moderate strength and maximum electrical conductivity.

Alum. Pipe Bus

Unit	Selection	Output
Bus Type
Size
Alloy

Alum. Pipe Bus Selections

Bus Type	Bus Size	Alloy (Pipe Only)

Alum. Cable Bus

Unit	Selection	Output
Cable Type
Size
# of Cond/Phase

Cable Bus Selections

Cable Type	Cable Size	Cable per Phase

Breaker Bus Configuration

A substation bus scheme is the arrangement of overhead bus bar and associated switching equipment (circuit breakers and isolators) in a substation. The operational flexibility and reliability of the substation greatly depends upon the bus scheme.

The first requirement of any substation design is to avoid a total shutdown of the substation for the purpose of maintenance, or due to fault somewhere out on the line. A total shutdown of the substation means complete shutdown of all the lines connected to the substation.

Clearly, a EHV or UHV transmission substation where a large number of critical lines terminate is extremely important, and the substation should be designed to avoid total failure and interruption of minimum numbers of circuits.

There are six common substation bus schemes that every engineer or designer should understand.

Breaker and a Half Scheme

The breaker-and-a-half configuration, typically used at extra-high-voltage (EHV) stations, consists of two buses, each normally energized. Electrically connected between the buses are three circuit breakers and, between each two breakers, a circuit, as shown in Figure F.2. In this arrangement, three circuit breakers are used in a bay for two independent circuits; hence, each circuit shares the common center circuit breaker, so there are 1.5 circuit breakers per circuit.

The breaker-and-a-half configuration provides for circuit breaker maintenance, since any breaker can be removed from service and isolated without interrupting any circuit. Additionally, faults on either of the main buses cause no circuit interruptions. Failure of a circuit breaker results in the loss of two circuits if a common breaker fails and only one circuit if an outside breaker fails. It is important to balance circuits in the bays, for example, source lines coming into the right-hand side of bays and load lines leaving the left-hand side of bays.
The main advantages of this scheme include the following:

A bus fault does not interrupt service on any circuit, and circuit breaker failure causes loss of only one or two circuits;

Flexible operation;

High reliability;

Double feed to each circuit.

The primary disadvantages of this scheme include the following:

One-and-a-half breakers are required per circuit.

Relaying is complex, since the center breaker has to respond to faults of either of its associated circuits, and since currents from two sources must be measured for all circuits;

High reliability.

Each circuit must have its own potential source for relaying.

Ring Bus Scheme

For stations having three to five circuits, a ring bus is often used. As more circuits are added, the configuration may evolve to a breaker-and-a-half arrangement. Figure shows a three-circuit ring bus that is based on Figure F.2 but with the bottom bay and three breakers and one bay-two circuit removed.

A maintenance outage of a circuit breaker or circuit causes an “Open ring.” For open-ring operation, a subsequent circuit outage may cause outage of additional circuits. The advantages of this scheme include:

Low cost—only one circuit breaker per circuit;

Flexibility to evolve to a breaker-and-a-half arrangements as more circuits are added.

The disadvantages of this scheme include:

Reduced reliability in open-ring operation.

Temptation to add circuits without evolution to a breaker-and-a-half arrangement.

Main Transfer Scheme

A main and transfer bus configuration consists of two independent buses, one of which, the main bus, is normally energized. Under normal operating conditions, all incoming and outgoing circuits are fed from the main bus through their associated circuit breakers and switches.

If it becomes necessary to remove a circuit breaker from service for maintenance or repairs, circuit operation can be maintained through use of the isolating switches and bus transfer equipment.
The circuit breaker to be maintained and its switches are opened, the bus transfer switches are closed, the switch from the transfer bus to the circuit is closed, and then the bus transfer breaker is closed to re-energize the circuit. The circuit is then protected by the bus transfer breaker. Figure F.1 shows the typical configuration of a main and transfer bus scheme. The main advantages of this scheme include:

Accommodation of circuit breaker maintenance while maintaining service and line protection;

Low cost—essentially one breaker per line or transformer;

Fairly small land area;

Easily expandable.

The primary disadvantages of this scheme include the following:

Failure of a circuit breaker or a bus fault causes loss of the entire bus with outage of all circuits.

An additional circuit breaker is required for bus tie.

Since the bus tie breaker has to be able to be substituted for any line breaker, its associated relaying may be complicated.

Complicated switching is required to remove a circuit breaker from service for maintenance.

The main and transfer bus scheme, which has the potential for a major outage of all circuits, is mainly used in older stations, most often at voltages of 230 kV and below. For large stations, the bus may be broken into two or three sections, with bus-sectionalizing circuit breakers.
A bus fault or breaker failure then affects only one section of bus, with the opening of the sectionalizing breakers preventing outages on other bus sections. It is important to distribute circuits onto bus sections in a balanced way, so that sufficient transmission network conductivity remains with a bus section outage.

Double Breaker Double Bus Breaker Scheme

The double breaker-double bus configuration consists of two main buses, each normally energized. Electrically connected between the buses are two circuit breakers and, between the breakers, one circuit. Two circuit breakers are required for each circuit.
In the double breaker-double bus configuration, any circuit breaker can be removed from service without interruption of any circuits. Faults on either of the main buses cause no circuit interruptions. Circuit breaker failure results in the loss of only one circuit.
>Because of high cost, the double breaker-double bus configuration is usually limited to large generating stations. The additional reliability afforded by this arrangement over the breaker-and-a-half scheme usually cannot be justified for conventional transmission or distribution substations. Occasionally, at a generating station, one bay of a breaker-and-a-half arrangement is used as a double breaker-double bus arrangement for a generator terminal to provide equal access to either main bus. The main advantages of this scheme include:

Flexible operation.

Very high reliability.

Isolation of either main bus for maintenance without disrupting service.

Isolation of any circuit breaker for maintenance without disrupting service.

Double feed to each circuit.

No interruption of service to any circuits from bus fault.

Loss of only one circuit for breaker failure.

Double feed to each circuit.

All switching with circuit breakers.

The primary disadvantage of this scheme is high cost because two circuit breakers are required for each circuit.

Double Bus Single Breaker Scheme

Substations utilizing this configuration are supplied with two busses. Each circuit is equipped with a single breaker and is connected to both buses using isolators.
A tie breaker connects both main buses and is normally closed, allowing for more flexibility in operation. A fault on one bus requires isolation of the bus while the circuits are fed from the opposite bus.
The double bus single breaker scheme is more expensive and requires more installation space than the single bus configuration. It is common to find this scheme with an additional transfer bus in EHV transmission substations.

Single Breaker Scheme

As the name implies, the sigle bus substation configuration consists of all circuits connected to a main bus. A fault on the bus or between the bus and circuit breaker will result in an outage of the entire bus or substation. Failure of a single circuit breaker will also result in an outage of the entire bus.
Maintenance of any circuit breaker requires shutdown of the corresponding circuit/line and maintenance of the bus requires a complete shutdown of the bus. A bypass switch across the breaker should be used for maintenance of the corresponding breaker. Circuit protection is disabled in this case.
The single bus substation configuration is the simplest and least expensive of all configurations. This configuration requires less installation area and it can be easily expanded.Single bus configurations are not considered reliable systems and they should only be implemented in substations where high reliability is not required, such as large transmission yards.
Reliability and availability of this system can be improved by expanding and sectionalizing the bus.

Breaker CAD/Export Generator

All breaker drawings, from breaker Single Lines, AC and DC Schematics, to Wiring Diagrams, can be generated from here!

Drawing Parameters

Orientation

Borders

Associated Drawings

Title Block Information

Project ID
Equipment ID

Date
Project Lead

Project Manager
Project Drawing ID

Disclaimer

The material contained in this Software is not intended as a representation or warranty on the part of Electrical Design Management (EDM) or any other person/organization named herein.

The material is for general information only. It is not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a relevant professional.

Anyone making use of the information set forth herein does so at his own risk and assumes any and all resulting liability arising there from.

Ref #	Designation	Breaker Device
1	87-1	Transformer T1 87-1 - Trip to Trip Coil 1
2	87-2	Transformer T1 87-2 - Trip to Trip Coil 2
3	86	Transformer T1 86 Lockout - Trip to Trip Coil 1