earthing switch that has the capability to: – make, carry and interrupt the induced current; – withstand the recovery voltage caused by electromagnetic and/or by electrostatic couplings
Scope
IEC 62271 specifies requirements for a.c high-speed earthing switches intended for both indoor and outdoor use, operating at service frequencies of 50 Hz and 60 Hz on systems with voltages of 550 kV and higher.
High-speed earthing switches described in this standard are intended to extinguish the secondary arc remaining after clearing faults on transmission lines by the circuit-breakers.
Normative references
This document references essential documents that are crucial for its application For references with specific dates, only the cited edition is applicable In the case of undated references, the most recent edition of the referenced document, including any amendments, is relevant.
IEC 62271-1:2007, High-voltage switchgear and controlgear – Part 1: Common specifications
IEC 62271-100:2008, High-voltage switchgear and controlgear – Part 100: Alternating-current circuit-breakers
IEC 62271-102:2001, High-voltage switchgear and controlgear – Part 102: Alternating current disconnectors and earthing switches
IEC 62271-203:2011, High-voltage switchgear and controlgear – Part 203: Gas-insulated metal-enclosed switchgear for rated voltages above 52 kV
2 Normal and special service conditions
Clause 2 of IEC 62271-1:2007 is applicable
For the purposes of this document, the terms and definitions given in Clause 3 of IEC 62271-1:2011, as well as the following apply.
General terms
3.1.101 secondary arc arc that remains at the faulted point after interruption of the short-circuit current fed by the network
Note 1 to entry: This secondary arc is supplied by electrostatic or electromagnetic induction from the adjacent healthy phases
3.1.102 single-phase auto-reclosing scheme auto-reclosing scheme in which a faulted phase circuit is opened and automatically re-closed independently from the other phases
The multi-phase auto-reclosing scheme, designated as 3.1.103, is implemented for double circuit overhead lines This system allows for the independent opening and re-closing of all faulted phase circuits, ensuring that at least two different phases remain un-faulted during the process.
Note 1 to entry: An example of multi-phase auto-reclosing scheme is indicated in Figure 1
1) Up to 4 phases have a fault Closed circuit-breaker
2) Only the faulted phases have been tripped Open circuit-breaker
3) All circuit-breakers at both ends re-closed Re-closed circuit-breaker
Figure 1 – Explanation of a multi-phase auto-reclosing scheme
A commonly used three-phase auto-reclosing scheme involves tripping and re-closing all three phases at both ends, regardless of whether a fault occurs in just one phase However, the application of high-speed earthing switches in this scheme remains infrequent.
A successive fault refers to an additional earth fault that takes place in the neighboring phase circuit(s) during the time period between a single-phase earth fault and the activation of the high-speed earthing switch(es).
Assemblies of switchgear and controlgear
Parts of assemblies
Switching devices
HSES earthing switch that has the capability to:
– make, carry and interrupt the induced current;
– withstand the recovery voltage caused by electromagnetic and/or by electrostatic couplings prior to circuit re-closure;
– make and carry the rated short-circuit current
Note 1 to entry: The high-speed operation applies normally to both closing and opening
Note 2 to entry: A high-speed earthing switch is not intended to be used as a maintenance earthing switch
3.4.103.1 high-speed earthing switch class M0 high-speed earthing switch having a normal mechanical endurance of 1 000 operation cycles
3.4.103.2 high-speed earthing switch class M1 high-speed earthing switch having an extended mechanical endurance of 2 000 operation cycles for special requirements
Parts of switchgear and controlgear
Operation
Characteristics quantities
Clause 4 of IEC 62271-1:2007 is applicable with the following additions
4.4 Rated normal current and temperature rise
Subclause 4.4 of IEC 62271-1:2007 is not applicable
4.101 Rated short-circuit making current
Subclause 4.101 of IEC 62271-102:2001 is applicable
The rated characteristics of the HSES are referred to the rated operating sequence a) C – t i1 – O or b) C – t i1 – O – t i2 – C – t i1 – O where
The time \( t_{i1} \) is defined as the duration exceeding the time necessary for secondary arc extinction and the dielectric recovery of air insulation at the fault location Users determine \( t_{i1} \) based on system stability considerations, with a recommended value of 0.15 seconds.
The intermediate time, denoted as \$t_{i2}\$, is determined by the system protection and encompasses the circuit-breakers' closing time after the High-Speed Earth Switches (HSESs) open, the duration of a new line fault, and the circuit-breakers' breaking time After this \$t_{i2}\$ period, the HSES can be safely reclosed, with a preferred value of \$t_{i2}\$ set at 0.5 seconds.
In this case the HSES shall be able to operate without intentional time delay
Figure 2 shows the time chart for the rated operating sequence of C – t i1 – O – t i2 – C – t i1 – O.
Current flow in HSES time
Circuit- breaker Transmission line circuit-breakers that interrupt the fault 3 Contact touch of HSESs
HSES High-speed earthing switches 4 Energizing of the opening release of the HSESs
1 Energizing of the closing circuit of the
HSESs 5 Contact separation of HSESs
2 Current start in HSESs 6 Arc extinction in HSESs t i1 , t i2 Times defined in 4.102 7 Fully open position of HSESs
NOTE 1 A common value for the re-closing time of the circuit-breaker is 1 s to guarantee system stability
NOTE 2 t i1 is normally within the range of 0,15 s to 0,5 s
NOTE 3 t i2 is normally within the range of 0,5 s to 1 s
NOTE 4 The operating sequence b) is for system stability requirements to cover cases where another fault occurs on the same phase
NOTE 5 The HSES closing time is normally less than 0,2 s
Figure 2 – Timing chart of HSES and circuit-breakers
Standard values for HSES are given in Table 1
Table 1 – Standardized values of rated induced currents and voltages
Rated voltage U r Electromagnetic coupling Electrostatic coupling
Rated power frequency recovery voltage ( - + 0 10 % )
Rated induced voltage ( - + 0 10 % ) kV A (rms) kV (rms) kV ms A (rms) kV (rms)
NOTE 1 For Table 1 the rated induced voltages by electrostatic recovery voltage have a 1-cos wave shape
NOTE 2 For networks with up to two faults (category 0 and 1 as described in B.2) the corresponding values are presented in Table B.3
For networks with delayed current zero crossing occurrence (category 3 as described in B.2), the corresponding values are presented in Table B.1
For networks with multi-phase faults (category 4 as described in B.2) the corresponding values are presented in Table B.2
Clause 5 of IEC 62271-1:2007 is applicable with the following modifications
Subclause 5.5 of IEC 62271-1:2007 is not applicable
5.7 Independent manual operation power operation (independent unlatched operation)
Subclause 5.7 of IEC 62271-1:2007 is not applicable
The designation of the equipment is specified as HSES
Items to be indicated on the nameplate are listed in Table 2
Table 2 – Items to be listed on nameplate of a HSES
The manufacturer specifies the designation of type and serial number, along with the year of manufacture Key electrical parameters include the rated voltage, rated lightning impulse withstand voltage, rated switching impulse withstand voltage, and rated power-frequency withstand voltage Additionally, the rated short-time withstand and peak withstand current, as well as the rated duration of short-circuit, are critical for performance assessment.
Rated filling pressure for insulation and /or operation Rated supply voltage of auxiliary circuit
Rated frequency Mechanical endurance class Mass (including fluid) Operating sequence
Subclause 5.11 of IEC 62271-1:2007 is not applicable
Anti-pumping device shall be provided for pneumatic and hydraulic operating mechanism
A High Voltage Electrical System (HSES) must effectively ground transmission lines and restore full voltage within the auto-reclosing duty cycle's dead time, typically around 1 second This dead time is crucial for system stability, allowing for the dielectric recovery of insulation at the fault site Additionally, the system requires rapid operational capabilities for both making and breaking connections.
The HSES shall have a capability to by-pass secondary arc current on the transmission lines
The HSES shall have a capability to break induced current by electromagnetic and/or electrostatic coupling on transmission lines with a recovery voltage specified in Table 1
The HSES shall have a capability to withstand transient recovery voltage after interruption and rated power frequency voltage to earth (U r /√3) in open position
The HSES shall be single-pole operated unless otherwise specified
Clause 6 of IEC 62271-1:2007 is applicable with the following additions
The dielectric performance shall be verified for phase-to-earth in the open position only in accordance with IEC 62271-1:2007
Subclause 6.1.1 of IEC 62271-1:2007 is not applicable
In case of metal enclosed type, 6.3 of CEI 62271-203:2011 is applicable
Subclause 6.5 of IEC62271-1:2007 is not applicable
6.101 Tests to prove the short-circuit making performance
Subclause 6.101 of IEC 62271-102:2001 is applicable
6.102 Operating and mechanical endurance tests
Subclause 6.102 of IEC 62271-102:2001 is applicable
The rated operating sequence shall be verified during mechanical operation
The mechanical operating sequence for class M0 shall be one of the following: a) A HSES with a specified duty cycle required C – t i1 – O:
– 1 000 C – t i1 – O operations b) A HSES with a specified duty cycle C – t i1 – O – t i2 – C – t i1 – O
For class M1 the number of operations shall be twice the sequence specified
Mechanical travel characteristics shall be recorded and acceptance criteria are referred to 6.101.1.1 of IEC 62271-100:2008 with the modification of the total tolerance to 20 % (for example - + 0 20 %, - + 10 10 % or - + 20 0 %)
6.103 Operation under severe ice condition
6.104 Operation at the temperature limits
6.105 Tests to prove the making and breaking performance of HSES
Tests shall be performed in accordance with the condition specified in Table 1
Subclause C.6.105 of IEC 62271-102:2001 is applicable with the following additions and modifications
Measurement of travel characteristics shall be in accordance with subclause 6.101.1.1 of IEC 62271-100:2008
Test circuits are those shown in Figures C.1 and C.2 of IEC 62271-102:2001
For electrostatic induced current test independent of the rated voltage of the HSES, the test circuit parameters shall be:
The HSES shall preferably be tested at rated frequency; however, for convenience of testing, tests at 50 Hz covers the requirement for 60 Hz and vice versa
These tests cover the classes of A and B described in Annex C of IEC 62271-102:2001
Type tests for HSES having a rated induced current making and breaking capability shall include tests to prove the electromagnetically and/or electrostatically induced current making and breaking capability
The test currents shall be within a tolerance of ( - + 0 10 %) of the rated induced currents as shown in Table 1
For effective testing, the control voltage of the HSES can be set to either the rated or maximum auxiliary supply voltage, provided it does not impact the making and breaking capability of the HSES This requirement is met if the travel characteristics remain within a range of ±5% compared to those achieved with the minimum control voltage.
Induced current making and breaking tests shall be conducted without maintenance
6.105.3 Arrangement of HSES before the test
The HSES being tested must be fully assembled on its designated support or an equivalent mechanical test support The operating device should be utilized according to specified guidelines, ensuring that if it is powered electrically, hydraulically, or pneumatically, it operates at either the minimum supply voltage or the minimum functional pressure required for its operation.
Before conducting making and breaking tests, it is essential to perform no-load operations and document the operating characteristics of the HSES, including travel characteristics, closing time, and opening time.
If applicable, tests shall be performed at the minimum functional pressure for interruption and insulation
6.105.4 Behaviour of HSES during the test
The HSES shall perform successfully without undue mechanical or electrical distress
During tests, HSES shall not
– show harmful interaction with adjacent laboratory equipment;
– exhibit behaviour which could endanger an operator
The emission of gases, flames, or metallic particles from the switch during operation is allowed, provided it does not compromise the insulation level of the earthing switch or pose a risk to the operator or nearby individuals.
Comparison of mechanical characteristics before and after the test shall be done according to subclause 6.102
Subclause C.6.105.9 of IEC 62271-102:2001 is applicable
Clause 7 of IEC 62271-1:2007 is applicable with the following additions
Mechanical operating test is to refer to subclause 7.101 of IEC 62271-100:2008
Mechanical travel characteristics shall be recorded and acceptance criteria are referred to subclause 6.101.1.1 of IEC 62271-100:2008 with the modification of the tolerance to 20 % (for example - + 0 20 % or - + 10 10 % or - + 20 0 %)
Timing test of close and open with rated and minimum conditions of auxiliary supply shall be verified
8 Guide to the selection of HSES
For the selection of HSES described in Table 1 and also Tables B.1 and B.2 if necessary, the following conditions and requirements at site shall be considered:
– auto-reclosing scheme (single or multi auto-reclosing scheme);
– the operating sequence is linked to circuit-breaker operating sequence;
– consideration on successive faults and other special conditions such as delayed current zero phenomena during HSES operations;
– required operational performance (mechanical endurance);
– switching requirements (fault making capability);
– class M1 is mainly for applications where the high-speed earthing switch is operated in special requirement where frequent lightning strokes occur;
9 Information to be given with enquiries, tenders and orders
Clause 9 of IEC 62271-1:2007 is applicable
10 Rules for transport, storage, installation, operation and maintenance
Clause 10 of IEC 62271-1:2007 is applicable
Clause 11 of IEC 62271-1:2007 is applicable
Background information on the use of HSES
Single-phase and multi-phase auto-reclosing schemes are utilized in high-voltage transmission systems to improve reliability In the event of an earth fault on an overhead line, circuit-breakers at both ends of the line activate to clear the fault.
In case of high-voltage overhead lines (especially for system voltages equal to or higher than
In 550 kV transmission systems with closely located single-phase conductors, a residual current known as secondary arc current can persist at the fault point after the short-circuit current is interrupted This secondary arc current arises from the electrostatic or electromagnetic coupling with adjacent live conductors and is challenging to extinguish quickly To enhance system stability, it is advisable to implement an auto-reclosing scheme with a maximum reclosing time of 1 second Effective measures must be taken to extinguish the secondary arc before the circuit-breakers are reclosed.
For short distance lines lacking shunt reactors or in double circuit systems with multi-phase auto-reclosing schemes, the use of a high-speed earthing switch (HSES) is essential for secondary arc extinction This specialized earthing switch is engineered for rapid operation to achieve the necessary switching performance, making it a crucial component in these applications.
The secondary arc extinction performance will be influenced by the recovery voltage and secondary arc current at the fault location, both of which will be influenced by the following:
The configuration of transmission towers, including options for single or double circuit lines, significantly impacts their design Key factors to consider are the distance between phases and circuits, as well as the height of the lines above ground level Additionally, the transposition of transmission lines, whether untransposed or transposed, plays a crucial role in optimizing performance and reducing electrical interference.
– occurrence of successive earth faults on the other line
Therefore the time duration between the duty cycles is specified by the user
NOTE This HSES is distinguished from a fast acting earthing switch Refer to Table A.1
The operating sequence of a High-Speed Emergency System (HSES) is influenced by several factors, including the time required to ensure system stability, the rapid auto reclosing sequence of the circuit-breaker, and the dielectric recovery characteristics at the fault point on the transmission line Additionally, it involves coordinating timing with protection relays, which includes confirming the open or close status of both the circuit-breaker and the HSES.
Figure A.1 shows a single line diagram of a power system A fault has occurred on one phase of the transmission line
CB 1 , CB 2 Transmission line circuit-breakers HSES 1 , HSES 2 High-speed earthing switches
Figure A.1 – Single-line diagram of a power system
The circuit-breakers at both ends of the line open to interrupt the fault current After 0.2 seconds, the High-Speed Earthing Switches (HSESs) close and remain closed for several hundred milliseconds, allowing secondary arc current to extinguish and insulation to be re-established The HSESs typically open 0.1 seconds after receiving the opening signal, with the first HSES interrupting electromagnetic induced current and the second interrupting electrostatic induced current The circuit-breaker will re-close once the HSESs have completed their opening operation.
Figure A.2 illustrates a typical timing chart depicting the interaction between transmission line circuit-breakers that interrupt faults and the HSESs, highlighting the initial O – C operation of the circuit-breakers and the subsequent C – O operation of the HSESs.
Circuit- breaker Transmission line circuit-breakers that interrupt the fault 3 Contact touch of HSESs
HSES High-speed earthing switches 4 Energizing of the opening release of the HSESs
1 Energizing of the closing circuit of the
HSESs 5 Contact separation of HSESs
2 Current start in HSESs 6 Arc extinction in HSESs
Figure A.2 – Timing chart of the HSESs in relation to the transmission line circuit-breakers
Successive fault occurs in the adjacent