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GB 1984-1989 AC high voltage circuit breakers

Basic Information

Standard ID: GB 1984-1989

Standard Name: AC high voltage circuit breakers

Chinese Name: 交流高压断路器

Standard category:National Standard (GB)

state:Abolished

Date of Release1989-03-21

Date of Implementation:1990-01-01

Date of Expiration:2004-01-01

standard classification number

Standard ICS number:Electrical Engineering>>Electrical Devices>>29.120.50 Fuses and other overload protection

Standard Classification Number:Electrical Engineering>>Power Transmission and Transformation Equipment>>K43 High Voltage Switchgear

associated standards

alternative situation:GB 1984-1980; replaced by GB/T 1984-2003

Procurement status:IEC 56-1987 NEQ

Publication information

other information

Drafting unit:Xi'an High Voltage Electrical Equipment Institute

Publishing department:Ministry of Machinery and Electronics Industry

Introduction to standards:

GB 1984-1989 AC high voltage circuit breaker GB1984-1989 standard download decompression password: www.bzxz.net

Some standard content:

National Standard of the People's Republic of China
Alternating current high-voltage circuit-breakers
Alternating current high-voltage circuit-breakers This standard adopts the international electrotechnical standard IEC56 "High Voltage Alternating Current Circuit Breakers" (1987 edition) with reference. 1 Subject content and scope of application
GB1984-89
Replaces GB1984-·80
This standard specifies the use environment conditions, terminology, rated parameters, design and structure, type test, factory test, information provided with inquiry form, tender and order form, transportation, storage, installation and maintenance rules and operation selection guidelines for indoor and outdoor three-pole or single-pole circuit breakers and their operating mechanisms and auxiliary devices. This standard applies to indoor and outdoor three-pole or single-pole circuit breakers and their operating mechanisms and auxiliary devices with a rated voltage of 3 to 500 kV and a frequency of 50 Hz. However, this standard does not allow the use of direct human operating mechanisms (except for human energy storage operating mechanisms) to close circuit breakers, which cannot guarantee the safety of personnel and equipment. Note: Certain specific requirements beyond this standard are specified by the corresponding professional standards; special requirements beyond this standard are negotiated between the user and the manufacturer. 2. Reference standards
GB11022
General technical conditions for high-voltage switchgear
GB2900.19
GB2900.20
Electrical terminologyBasic terminology
High voltage test technology and insulation coordination
Electrical terminology
High voltage switchgear
Electrical terminology
Insulation coordination of high-voltage power transmission and transformation equipment
GB311.1~311.6
GB4474
GB4876
GB7675
GB5273
GB2706
GB3309
GB7354
High voltage test technology for near-field fault test of AC high-voltage circuit breakers
AC Line charging current opening and closing test of high-voltage circuit breakersOpening and closing test of AC high-voltage circuit breakersTest of capacitor banksConnection terminals of transformers, high-voltage electrical appliances and bushingsHeating of AC high-voltage electrical appliances during long-term operationTest methods for dynamic and thermal stability of AC high-voltage electrical appliancesMechanical test of high-voltage switchgear at room temperatureMeasurement of partial discharge
GB11604
GB4473
GB11023
GB1985
Test methods for radio interference of high-voltage electrical equipmentSynthetic test of AC high-voltage circuit breakers
Guide for sulfur hexafluoride gas sealing test of high-voltage switchgearAC high-voltage disconnectors and earthing switches
GB7674
Test methods for artificial pollution migration of high-voltage insulators for AC systemsSulfur hexafluoride enclosed combination electrical appliances
Environmental conditions for use
According to the provisions of GB11022.
Approved by the Ministry of Machinery and Electronics Industry of the People's Republic of China on March 21, 1989 Solid Layer Method
Implemented on January 1, 1990
4 Terminology
GB1984-89
In addition to the relevant standards, the terms used in this standard are quoted in the following clauses as needed, and some clauses are supplemented or revised as necessary, and the time parameters therein are illustrated with diagrams. 4.1 Transient recovery voltage (TRV)
The recovery voltage with significant transient characteristics that appears on the contacts of the circuit breaker after the arc of the circuit breaker is extinguished. This voltage depends on the characteristics of the circuit and the circuit breaker, and is composed of the superposition of the power frequency component and the transient component (which can be non-periodic, single-frequency or multi-frequency oscillation).
The transient recovery voltage in a three-phase system refers to the first phase to be disconnected. 4.2 Initial transient recovery voltage (ITRV)
The initial part of the transient recovery voltage. At this time, the reflection of the wave from the first major discontinuity point along the busbar causes a small amplitude initial oscillation, and its oscillation amplitude is proportional to the busbar wave impedance and short-circuit current. Note: The initial transient recovery voltage is a physical phenomenon similar to the near-field fault pole, and is mainly determined by the busbar and line layout structure of the substation. 4.3 Specified value of expected transient recovery voltage
The limit value of the inherent transient recovery voltage of various circuits that the circuit breaker should be able to break under the specified short-circuit current and test mode. 4.4 Power frequency recovery voltage
The effective value of the recovery voltage after the transient recovery voltage between its contacts disappears after the arcs of all poles of the circuit breaker are extinguished. The value of the power frequency recovery voltage is determined by the vertical distance from the second half-wave peak of the recovery voltage waveform in the oscillogram to the connecting line of the first and third half-wave peaks in the time interval from 1/2f to 1/f after the arcs of all poles are finally extinguished. For the power frequency recovery voltage of a three-pole circuit breaker, it is determined by the arithmetic mean of the power frequency recovery voltage of each pole. The effective value of the power frequency recovery phase voltage U./3 of a three-pole circuit breaker is specified by the following formula: Us=(V,+V,+V.)
/33×2×/2×/3
When a three-pole circuit breaker is tested for three phases, it can also be expressed by the effective value of the power frequency recovery line voltage, which is U. 3
GB1984-89
Third floor
Figure 1 Determination of the power frequency recovery voltage of a three-pole circuit breaker 00 line - the moment when the arc is finally extinguished in each pole; G, G line - 1/2 moment after 00 moment; GzGz line - 1/F moment after 00 moment; V,, V, Vs - twice the peak value of the rated power recovery voltage of each pole; a frequency of the test circuit current Note; the arc of the first pole in the figure is extinguished first. 4.5 Opening time
For a circuit breaker in the closed position, the time interval from the moment the opening circuit is energized (i.e., receiving the opening command) to the moment when the arc contacts of all poles are separated.
The opening time of the circuit breaker is defined according to the following tripping methods (any time delay device that forms an integral part with the circuit breaker is adjusted to the minimum setting value):
a. For a circuit breaker that uses any form of auxiliary power for tripping, the opening time refers to the time interval from the moment the opening release is energized to the moment when the arc contacts of all poles are separated for the circuit breaker in the closed position; b. For a circuit breaker that uses the main circuit current without any form of auxiliary power for tripping, the opening time refers to the time interval from the moment the main circuit current reaches the operating current of the overcurrent release to the moment when the arc contacts of all poles are separated for the circuit breaker in the closed position.
Note: ① For circuit breakers equipped with parallel resistors, a distinction should be made between the opening time until all arc contacts are separated and the opening time until all series contacts with parallel resistors are separated. Unless otherwise specified, the opening time refers to the time until the main arc contacts are separated. ② The opening time can vary significantly with the breaking current. ③ For circuit breakers equipped with multiple arc extinguishing units per pole, the moment when all arc contacts of all poles are separated is determined by the moment when the contacts of the first breaking unit of the last pole to be separated are separated.
④ The opening time includes the operating time of any auxiliary equipment that is necessary for the circuit breaker to open and forms an integral part of the circuit breaker. 4.6 Arcing time
The time interval from the moment when the main circuit contacts of the first separated pole just break away from electrical contact to the moment when the arcs in each pole are finally extinguished. 4.7 Breaking time
The time interval from the moment when the circuit breaker receives the opening command to the moment when the arcs in each pole are finally extinguished. Note: Generally equal to the sum of the opening time and the arcing time. 4.8 Closing time
According to Article 6.42 of GB2900.20.
4.9 Closing time
According to Article 6.43 of GB2900.20.
4.10 Pre-breakdown time
According to Article 6.38 of GB2900.20.
4.11 Automatic reclosing operation
According to Article 5.7 of GB2900.20.
4.12 Open-close time (when automatic reclosing) is in accordance with Article 6.44 of GB2900.20.
4.13 No-current time (automatic reclosing) shall be in accordance with Article 6.45 of GB2900.20.
4.14 Reclosing time
shall be in accordance with Article 6.47 of GB2900.20.
4.15 Reclosing time (reclosing)bzxz.net
shall be in accordance with Article 6.46 of GB2900.20.
4.16 Closing-breaking time
shall be in accordance with Article 6.48 of GB2900.20.
4.17 Closing-breaking time
shall be in accordance with Article 6.49 of GB2900.20.
Note: For the illustration of time parameters, see Figures 2 to 7. GB1984-89
4.18 Back-to-back capacitor bank (multiple parallel capacitor banks) A group of capacitors or capacitor combinations in parallel, each unit of which can be independently put into or out of the power system. The capacitors that have been connected to the power supply will significantly increase the inrush current and electric power of the unit. 4.19 Interconnection circuit breaker
Used to connect two independent power systems, in addition to circuit breakers with general characteristics, it should also have circuit breakers with specified out-of-step breaking, closing and insulation performance.
Required position
Closing circuit energized
Closing position
1 minute time
Current flows
Breaking time
Dividing circuit breaker energized
Separation position
Closing time
Usage time
Combine circuit energized
GB1984-89
Contact movement
Ground source time
Surge operation
Arcs in all poles finally extinguish
Strong contacts in all poles separate
General contact movement
Current flows
Separation position
Closing position
Closing operation
Pre-breakdown time
All poles Contact in the middle
Electro-hydraulic begins to flow in the first pole
Circuit breaker without opening and closing resistors
Required closing position
Closure-open time
4.17 Breaking time
Contact in all poles
Current begins to flow in the first pole
Opening and closing operation
Contact movement
Electric intensity in all poles finally extinguishes
Separation of contacts in all poles
Figure 3 Circuit breaker without opening and closing resistors
Closure-open cycle
Closure position
Current flows
Contact movement
1No current time
Open-close time
Reclosing time
"Reclosing" Switch time!
The electric intensity in all poles is finally extinguished
Arc contacts in all poles are separated
Opening release is energized
GB1984-89
Discretion position
Current flows
Contacts in all poles are in contact
Contacts in the first pole are in contact
Current begins to flow in the first pole
Figure 4 Reclosing position of circuit breaker without opening and closing resistors (automatic reclosing) in stages
Closing and disconnecting circuit is energized
Closing position
1 Stage time
Breaking time
Current flows
GB1984-89
Contact movement
Egg burning time!
Discretion operation||t t||1 All poles are extinguished
Cell current
Full current
All plates have strong contacts separated
Dividing release is energized
Dividing position
! Closing time
Closing time
Closing circuit is energized
Contact movement
Current flows
Dividing position
Closing position
Closing operation
4.10 Pre-breakdown time
All poles are in contact
Current starts to flow in the first plate
Full current
Resistance current
Circuit breaker with opening and closing resistors
Closing position
Current
14,16. 4.17 Closing-breaking time
Contacts in all poles in contact
Current starts to flow in the first plate
Full electro-hydraulic
Electric current
Opening and closing operation
Contact movement
Electricity in all poles is extinguished
Resistance electro-hydraulic
Full current
Arc contacts in all poles are separated
Figure 6 Circuit breaker with opening and closing resistors
Close-open cycle||tt| |Closing position
Current flows
Reclosing time,
Reclosing time
Contact movement
No current time
Open-close time
All poles power supply filter off
Full current
All poles open contacts are separated
Separation release is energized
GB198489
Required position
7 Circuit breaker with opening and closing resistors
Rated parameters||t t||Rated parameters that should be given for all circuit breakers: a.
Rated voltage and maximum voltage;
Rated insulation level;
Rated frequency;
Rated current:
Rated short-time withstand current (rated thermal stability current); Rated peak withstand current (rated dynamic stability current); Current flows through
Contacts in all poles touch
Contacts in the first pole touch
Current starts to flow through the pole
Full current
Resistance Electro-hydraulic
reclosing switch (automatic reclosing switch)
rated short-circuit duration (rated thermal stability time), except for circuit breakers equipped with direct overcurrent release; rated operating voltage of closing and opening operating mechanisms and rated voltage and rated power of auxiliary circuits; rated pressure of operating and arc-extinguishing gases (if applicable); rated short-circuit breaking current;
rated short-circuit making current;
specified value of expected transient recovery voltage;
rated operating sequence;
rated time parameters.
The rated parameters of circuit breakers used in the following special occasions should be given: 0.
Rated parameters for local faults, only for three-pole circuit breakers with rated voltage of 63kV and above and rated short-circuit breaking current exceeding 12.5kA and directly connected to overhead lines;
Rated line charging breaking current, only for three-pole circuit breakers with rated voltage of 110kV and above and used for opening and closing overhead lines, and can be extended to 35kV and 63kV circuit breakers when necessary; q.
Rated out-of-step breaking current, only for tie circuit breakers; rated cable charging breaking current;
Rated single capacitor bank breaking current;
Rated back-to-back capacitor bank breaking current; rated capacitor bank closing inrush current;
Rated induction motor breaking current;
Rated no-load transformer breaking current;
Rated reactor breaking current.
5.1 Rated voltage and maximum voltage
GB 1984--89
The rated voltage and maximum voltage shall be selected in accordance with Article 5.1 of GB11022. 2 Rated insulation level
According to Article 5.4 of GB11022.
5.3 Rated frequency
The rated frequency is 50Hz.
5.4 Rated current
200400,630,1000,1250,1600(1500),2000,2500,3150(3000),4000,5000,6300,800010000,12500,16000,20000A.
Note: ①The values ​​in brackets are only for old products. 1) Use as little as possible.
If the circuit breaker is equipped with a direct overcurrent release in series, the rated current should be the effective value of the current that the overcurrent release can pass for a long time without damage at the rated frequency, and the temperature rise does not exceed the specified value. 5.5 Rated short-time withstand current (rated thermal stability current) The rated short-time withstand current is equal to the rated short-circuit breaking current (see Article 5.11 of this standard). 5.6 Rated peak withstand current (rated dynamic stability current) The rated peak withstand current is equal to the rated short-circuit closing current (see Article 5.12 of this standard). Rated short-circuit duration (rated thermal stability time) 5.7
According to Article 5.6 of GB11022.
For circuit breakers equipped with direct overcurrent releases, the rated short-circuit duration does not need to be specified. However, when the circuit breaker is operated according to its rated operating sequence and the overcurrent release is set at the maximum time delay, the circuit breaker should be able to pass the rated short-circuit breaking current during the breaking time. 5.8 The rated operating voltage of the closing and opening operating mechanism and the rated voltage of the auxiliary circuit shall comply with Article 5.8 of GB11022.
5.9 The rated power supply frequency of the closing and opening operating mechanism and the auxiliary circuit is 50Hz.
) Rated gas pressure (gauge pressure) of compressed gas for operation and arc extinguishing 5.10
The rated gas pressure of compressed air circuit breakers and pneumatic mechanisms shall comply with Article 5.9 of GB11022. The rated pressure of sulfur hexafluoride gas in sulfur hexafluoride circuit breakers (corresponding to the rated density of sulfur hexafluoride at 20°C) is: 0.15, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70 MPa. 5.11 Rated short-circuit breaking current
The rated short-circuit breaking current is the maximum short-circuit current that the circuit breaker can break under the corresponding power frequency and transient recovery voltage specified in this standard. It is represented by two characteristic values:
a. The effective value of the AC component, referred to as "rated short-circuit current"; b. The percentage of the direct component.
Note: If the DC component does not exceed 20%, the rated short-circuit breaking current is only characterized by the effective value of the AC component. For the determination of AC and DC components, refer to Figure 8. 5.11.1 Effective value of AC component of rated short-circuit breaking current Effective value of AC component of rated short-circuit breaking current is selected from the following values: 1.6, 3.15, 6.3, 8, 10, 12.5, 16, 20, 25, 31.5, 40, 5063, 80, 100kA Note: For those exceeding 100kA, the value is extended according to the R10 series. GB1984—89
5.11.2 Percentage of DC component of rated short-circuit breaking current The percentage of DC component is generally taken from Figure 9. The value of "" in the figure is determined as follows: For circuit breakers directly tripped by short-circuit current, the value of "" is equal to the specified opening time; a.
For circuit breakers tripped only by auxiliary energy, the value of "" is equal to the specified opening time plus 0.01s. b.
Note: In some cases, such as circuit breakers close to generators, a larger percentage of DC component than given in the figure may be required, and its value is determined by the supplier and the buyer.
Rated short-circuit making current
The rated short-circuit making current (peak value) of the circuit breaker is 2.5 times the effective value of the AC component of its rated short-circuit breaking current. See Figure 8. E
Figure 8 Determination of short-circuit closing, breaking current and DC component percentageAA', BB\-current waveform envelope; BX-normal neutral line; CC\-offset of any instantaneous current waveform zero line; EE\--contact separation moment (arc starting moment); DD-any instantaneous current AC component effective value measured from CC\; IMc-closing current; IAc\-EE\ instantaneous current AC component peak value; IAc2-EE' instantaneous IX100
current AC component effective value; Ix\-EE\ instantaneous current DC component: -percentage of DC component
time interval from the start of short-circuit current:, mFigure 9 Relationship between DC component percentage and time interval r3 Expected transient recovery voltage (when the outgoing line is short-circuited) 5.13
The expected transient recovery voltage when the outgoing line is short-circuited is the transient recovery voltage limit value of the circuit that the circuit breaker should be able to break under the condition of outgoing line short-circuit.
5.13.1 Representation of transient recovery voltage waveform When the power system voltage is equal to or higher than 110 kV and the short-circuit current is relatively large, the transient recovery voltage is suitable for being represented by an envelope consisting of three segments determined by the four-parameter method. When the power system voltage is lower than 110 kV, or the voltage is higher than 110 kV but the short-circuit current is relatively small, and the power supply is supplied through a transformer under the condition of GB1984-89
, the transient recovery voltage is close to a damped single-frontal oscillation wave, and the transient recovery voltage is suitable for being represented by an envelope consisting of two segments determined by the two-parameter method.
Due to the influence of the local capacitance on the power supply side of the circuit breaker, a lower voltage rise rate is generated in the first few microseconds of the transient recovery voltage, and a time delay is introduced to consider this influence.
In some cases, due to the reflected wave along the first major discontinuity point of the busbar, a low-amplitude initial oscillation is caused, so the initial transient recovery voltage (ITRV) is introduced to consider this influence. ITRV is mainly determined by the busbar and busbar bay structure of the substation, and is a physical phenomenon similar to a near-field fault.
If the circuit breaker has a near-field fault test requirement, as long as the near-field fault test is conducted with a line without time delay, the ITRV requirement is considered to have been met.
Since ITRV is proportional to the busbar wave impedance and current, the ITRV requirement can be ignored for metal-enclosed switchgear with a small wave impedance and all switchgear with a rated short-circuit breaking current of less than 25kA. 5.13.2 Characteristic parameters representing transient recovery voltage The transient recovery voltage is represented by the following parameters: a.
Four-parameter method (see Figure 10)
First reference voltage, kV;
Time to reach u, us,
Second reference voltage (TRV peak), kV;
—Time to reach u, us;
Two-parameter method (see Figure 11)
Reference voltage (TRV peak), kV;
Time to reach u, us;
Transient recovery voltage delay line (see Figures 10 and 11) ta
Time delay, us;
u'reference voltage, kV;
t——Time to reach u, μs.
Initial transient recovery voltage (ITRV) (see Figure 12) - reference voltage (ITRV peak), kV;
Time to reach u:, us.
The rate of rise of ITRV depends on the short-circuit current being interrupted, and its amplitude depends on the distance along the bus to the first discontinuity. The rated ITRV is represented by two straight lines, the first is a straight line from the origin to (ui, t), and the second is a horizontal line from point (u;, t;) that intersects the time delay line of TRV at point A.
Time t
The specified transient recovery voltage (TRV) is represented by the four-parameter reference line and the time delay line Figure 101. Representation of transient recovery voltage waveform When the power system voltage is equal to or higher than 110kV and the short-circuit current is relatively large, the transient recovery voltage is suitable for the envelope composed of three segments determined by the four-parameter method. When the power system voltage is lower than 110kV, or the voltage is higher than 110kV but the short-circuit current is relatively small, and the power supply is supplied through the transformer under the condition of GB1984-89
, the transient recovery voltage is close to a damped single-frontal oscillation wave, and the transient recovery voltage is suitable for the envelope composed of two segments determined by the two-parameter method.
Due to the influence of the local capacitance on the power supply side of the circuit breaker, a lower voltage rise rate is generated in the first few microseconds of the transient recovery voltage, and a time delay is introduced to consider this influence.
In some cases, due to the reflection wave along the first major discontinuity point of the busbar, a low-amplitude initial oscillation is caused, so the initial transient recovery voltage (ITRV) is introduced to consider this influence. ITRV is mainly determined by the busbar and busbar bay structure of the substation, and is a physical phenomenon similar to a near-field fault.
If the circuit breaker has a near-field fault test requirement, as long as the near-field fault test is conducted with a line without time delay, the ITRV requirement is considered to have been met.
Since ITRV is proportional to the busbar wave impedance and current, the ITRV requirement can be ignored for metal-enclosed switchgear with a small wave impedance and all switchgear with a rated short-circuit breaking current of less than 25kA. 5.13.2 Characteristic parameters representing transient recovery voltage The transient recovery voltage is represented by the following parameters: a.
Four-parameter method (see Figure 10)
First reference voltage, kV;
Time to reach u, us,
Second reference voltage (TRV peak), kV;
—Time to reach u, us;
Two-parameter method (see Figure 11)
Reference voltage (TRV peak), kV;
Time to reach u, us;
Transient recovery voltage delay line (see Figures 10 and 11) ta
Time delay, us;
u'reference voltage, kV;
t——Time to reach u, μs.
Initial transient recovery voltage (ITRV) (see Figure 12) - reference voltage (ITRV peak), kV;
Time to reach u:, us.
The rate of rise of ITRV depends on the short-circuit current being interrupted, and its amplitude depends on the distance along the bus to the first discontinuity. The rated ITRV is represented by two straight lines, the first is a straight line from the origin to (ui, t), and the second is a horizontal line from point (u;, t;) that intersects the time delay line of TRV at point A.
Time t
The specified transient recovery voltage (TRV) is represented by the four-parameter reference line and the time delay line Figure 101. Representation of transient recovery voltage waveform When the power system voltage is equal to or higher than 110kV and the short-circuit current is relatively large, the transient recovery voltage is suitable for the envelope composed of three segments determined by the four-parameter method. When the power system voltage is lower than 110kV, or the voltage is higher than 110kV but the short-circuit current is relatively small, and the power supply is supplied through the transformer under the condition of GB1984-89
, the transient recovery voltage is close to a damped single-frontal oscillation wave, and the transient recovery voltage is suitable for the envelope composed of two segments determined by the two-parameter method.
Due to the influence of the local capacitance on the power supply side of the circuit breaker, a lower voltage rise rate is generated in the first few microseconds of the transient recovery voltage, and a time delay is introduced to consider this influence.
In some cases, due to the reflection wave along the first major discontinuity point of the busbar, a low-amplitude initial oscillation is caused, so the initial transient recovery voltage (ITRV) is introduced to consider this influence. ITRV is mainly determined by the busbar and busbar bay structure of the substation, and is a physical phenomenon similar to a near-field fault.
If the circuit breaker has a near-field fault test requirement, as long as the near-field fault test is conducted with a line without time delay, the ITRV requirement is considered to have been met.
Since ITRV is proportional to the busbar wave impedance and current, the ITRV requirement can be ignored for metal-enclosed switchgear with a small wave impedance and all switchgear with a rated short-circuit breaking current of less than 25kA. 5.13.2 Characteristic parameters representing transient recovery voltage The transient recovery voltage is represented by the following parameters: a.
Four-parameter method (see Figure 10)
First reference voltage, kV;
Time to reach u, us,
Second reference voltage (TRV peak), kV;
—Time to reach u, us;
Two-parameter method (see Figure 11)
Reference voltage (TRV peak), kV;
Time to reach u, us;
Transient recovery voltage delay line (see Figures 10 and 11) ta
Time delay, us;
u'reference voltage, kV;
t——Time to reach u, μs.
Initial transient recovery voltage (ITRV) (see Figure 12) - reference voltage (ITRV peak), kV;
Time to reach u:, us.
The rate of rise of ITRV depends on the short-circuit current being interrupted, and its amplitude depends on the distance along the bus to the first discontinuity. The rated ITRV is represented by two straight lines, the first is a straight line from the origin to (ui, t), and the second is a horizontal line from point (u;, t;) that intersects the time delay line of TRV at point A.
Time t
The specified transient recovery voltage (TRV) is represented by the four-parameter reference line and the time delay line Figure 10
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