1. Incompatibility between MV Switchgear conforming TO the international standards and their use in DNO’s substations
M. Arens – Y Tits – Belgium – Session 1 – Paper 0950

2. Distribution network criteria
MV switchgear has to meet the following criteria :
Network’s real service conditions
Network use
Load current capacity under high ambient temperature
Service continuity
M. Arens – Y Tits – Belgium – Session 1 – Paper 0950

3. Network’s real service conditions
Substation in the humid countryside without heating
Substation in cellar (P)
Metallic substation
 High temperature
 Low temperature
 Moisture
M. Arens – Y Tits – Belgium – Session 1 – Paper 0950

4. Network use
Connection of cable with cross section according to Irswitchgear :
Ir = 630 A  Cable section = 630 mm² Al
Ir = 800 A  Cable section = 2x400 mm² Al
 mechanical stress on the connection during connection work and during temperature rise and short circuit (expansion )
Few operations (except for smart grid application)
 higher forces for switching operations
M. Arens – Y Tits – Belgium – Session 1 – Paper 0950

5. Load current capacity for high ambient temperature
Generally low load current
Peak current for some hours in emergency situation
M. Arens – Y Tits – Belgium – Session 1 – Paper 0950

6. Service continuity Very high cost of outage Maintenance free
Cost of outage due to cable or switchgear failure
Cost of operation to liberate the installation
Maintenance free
M. Arens – Y Tits – Belgium – Session 1 – Paper 0950

7. Modes of ageing
Corrosion of metal parts under the influence of humidity and heat
Degradation of the insulating parts under the influence of moisture, heat and dielectric stress
Tightness of the vessel containing
the insulation gas mainly
influenced by temperature
M. Arens – Y Tits – Belgium – Session 1 – Paper 0950

8. Standards: implemented improvements
Example of improvement implemented in the last IEC
Stress on interlock mechanism:
attempt to operate the switching device in the wrong direction with a prospective force of 750 N
M. Arens – Y Tits – Belgium – Session 1 – Paper 0950

9. Standards: examples of needed improvements
Normal service conditions IEC should include:
Use for network service conditions
Consequently define required type tests
60587 Tracking test
but with increased number of cycles, HV impuls test and
PD measurements
Salt mist
Tightness at 40°C
M. Arens – Y Tits – Belgium – Session 1 – Paper 0950

10. Standards: examples of needed improvements
Other required type tests
Temperature rise test and short circuit test to perform with a representative cable connection
Dielectric test on SWG equipped with all accessories ( connection points
for cable test)
M. Arens – Y Tits – Belgium – Session 1 – Paper 0950

11. Standards: examples of needed improvements
Additional design criteria to be taken into account:
Possibility to respect EN for maintenance purposes (appropriate interlockings)
Required accessories for test purposes
arc suppressors are not addressed
Active parts outside the enclosure are not addressed
M. Arens – Y Tits – Belgium – Session 1 – Paper 0950

12. Conclusions Need to specify the DNO requirements
 discussion and preparation between DNO
 more implication of DNO in normative working groups
M. Arens – Y Tits – Belgium – Session 1 – Paper 0950