pressure switch internal arc presentation
DESCRIPTION
Pressure Switch Internal Arc PresentationTRANSCRIPT
Power Transmission and Distribution
Pressure Dependant Internal Arc Detection System
Product: Pressure Switches
s
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Unwanted
intruders & faulty
Operations
can
cause
Internal Arc
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Unwanted
results
1. Loss of Life
2. Loss of Revenue
Internal Arc
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Internal Arc
Arc inCable Compartment
Arc inBreaker Compartment
Arc inBusbar Compartment
Effects of Internal Arc in Medium Voltage Switchgear
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31.5kA Internal Arc for 1sec. in cable compartment
~ 9 ms 100 ms
~ 600 hPa
Pressure Characteristic of Arc Fault
Arc Initiation
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31.5kA Internal Arc for 1sec.in breaker compartment
~ 7 ms
~ 800 hPa
Pressure Characteristic of Arc Fault
100 ms
Arc Initiation
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31.5kA Internal Arc for 1sec.in bus bar compartment
680 hPa
Pressure Characteristic of Arc Fault
~ 7 ms
Arc Initiation100 ms
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Pressure Characteristic of Arc Fault
1. Highest steep fronted pressure wave within first 10 ms
2. Steep fronted pressure wave causes severe stress to theswitchgear
3. Thermal phase after 100 ms.
4. During thermal phase material melts, vaporises and decomposes.Will result in fire producing hot gases and decomposed products
~ 10 ms100 ms
Thermal phase
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Effect of Thermal Phase
Material melts, vaporises and decomposes
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Effect of Thermal Phase
... can also cause major fire if heavy insulation is used
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Use of insulation
Slight Considerable
Approx. 100 ms after ignition of the arc
Effect of Thermal Phase
Effect of thermal phase increases with increase in insulation
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Most Popular Arc Detecting Systems
Effect of thermal phase can be prevented by early detection of arc and isolating the switchgear within 100 mS.
Most popular arc detection sensors:
1. Pressure: Reacts to the increasing pressure
2. Light: Reacts to the light
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Sensors: Pressure Dependant
Pressure switcheswith tubes as sensors
Test Unit(Optional)
Trip Lock-out relay(Optional)
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Sensors: Light Dependant
Components:
1. Photo diode as sensor2. Connection between the sensors and slave unit3. Slave unit to transfer the signal to Master Unit4. Master unit to prevent unnecessary tripping
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Comparison of Arc Detecting Systems
Pressure Light
Detection of Pressure peak Increase of light intensityarc faults (dynamic) (dynamic)
Required 1. Sensor: A simple tube 1. Sensor: Photo diode incomponents in each MV compartment each compartment
and the respective switch (light is transformed into in LV compartment current)
2. Not applicable 2. Band pass filter +amplifier(Slave unit) + optionallyMaster unit
3. Tripping Lock-out relay 3. Tripping Lock-out relay(Optional) (Optional)
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Pressure Light
Electromagnetic No electric wires Questionable, as photo interference within the H.V. part diodes in MV compartment.
Otherwise optical fibres arerequired
Reliability against System reacts only System is sensitive againstunwanted operation on pressure rise in other light effects. Hence
case of an arc fault master unit wired with overcurrent protection is also required
System test Simple test device Photo flash light. Access to(bottle with pressure MV compartment necessarygauge) - Optional
Comparison of Arc Detecting Systems
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Comparison of Arc Detecting Systems
Pressure Light
Criteria for Direct signal from Signal from master unitbreaker tripping pressure switch or and additionally from
optionally through over current relay totripping lock-out relay avoid false tripping.
Optionally tripping relaycan be used in addition
Selective detection Possible, depending on Limited possibility as of arc faults type of switchgear with light can enter the(increase of availability) Compartment walls adjacent compartments
resistant to pressure activating the respectivee.g.. NXAIR sensors
Installation cost Economical Expensive
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Comparison of Arc Detecting Systems
We recommend Pressure dependant system:
1. More reliable than lightdependent system due to lessinterfaces
2. No compromise on technicalrequirements
3. On line testing possible as option
4. Less expensive compare to light dependent system
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Pressure Switch Assembly
1. Pressure switches mountedin Low Voltage Chamber.
2. All switches are tested before the delivery to switchgear manufacturer
3. Total maintenance free
4. Do not require any testing/supervision at site
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Pressure Switch Assembly
Optionally online testing version also available
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Operating pressure of pressure switch 10 ± 0,75 hPa
Reset pressure of pressure switch 3 ± 0,75 hPa
Minimum arc current for reliable operation ( for Compartment volume > 1,3 m3 )
4 kA
Response time of pressure switch 10-20 ms
Response time of Tripping lock-out relay ( Optional tripping )
< 15 ms
Break time of 3AH, 3AJ, 3AK VCB with 1st shunt release
< 80 ms
Break time of 3AH, 3AJ VCB with 2nd shunt release < 65 ms
Break time of 3AK VCB with 2nd shunt release < 60 ms
Pressure Switch Technical Data
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Pressure switch timings
75 80 85 90 95 100 105
1. VCB with Normal trip coil and direct tripping from pressure switch
2. VCB with Fast trip coil and tripping through inter tripping relay*
3. VCB with Fast trip coil and direct tripping from pressure switch
Maximum arc duration in ms
1.
2.
3.
Arcing time limited to 100ms
*: Tripping lock-out relay recommended for blocking the subsequent closing of Incomers and Bus-sectionaliser
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Example-1: Pressure switch assembly in NXAIR
1. Tripping lock-out relay (Optional)
2. Pressure switches
3. Tubes
P>P>P>P>
E
D
C
B
R 1
2
3
DruckschalterrelaisPessure switch relay
SchlauchleitungTube
DruckschaltersystemPessure switchsystem
A SammelschienenraumBusbar compartment
B AnschlussraumConnection compartment
A
C ModulraumModule compartment
D Zusatzraum für Anbauten an der Sammelschiene (Option)Additionalcompartment for busbar fittings(optional)
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Pressure switch wiring in NXAIR
Example: NXAIR: 12kV, 25kA( 3 compartments)
1. Each medium voltage compartment with individualpressure switches: B70, B71, B72
2. Pressure switches in Busbar andcircuit breaker compartment loopedtogether to trip the Incomer andbus-sectionaliser
3. Selective shutdown can be restricted to affected outgoing feeder due to confinement of internal arc and bushing type CT properties of NXAIR
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Example-2: Pressure switch assembly in SIMOPRIME
P>P>P>
E
C
R 1
2
3
DruckschalterrelaisPessure switch relay
SchlauchleitungTube
DruckschaltersystemPessure switchsystem
1. Tripping Lock-outrelay (Optional)
2. Pressure switches
3. Tubes
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Pressure switch wiring
Example: SIMOPRIME
1. Each medium voltage compartment with individualpressure switches: B70, B71, B72
2. Pressure switches in Busbar,circuit breaker and cable compartment looped together to trip the Incomer andbus-sectionaliser
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Conclusion
1. If the switchgear and control gear is installed, operatedand maintained as per the instructions of manufacturer,there should be little probability of internal arc occurringduring its entire service life, but is can not be completelydisregarded
2. Internal arc qualified switchgear as per IEC62271-200will offer the highest personal safety within the periodfor which switchgear has been tested
3. To reduce the thermal phase effects, arc detecting systemlimiting the arc within 100ms can be employed as option
4. If early arc detection system is desired, then systembased on Pressure is recommended