IEC 62271-200 - HV Swi tchgear And Contro lgear

IEC 62271-200 - HV Switchgear And Controlgear | EEPelectrical-engineering-portal.com /iec-62271-200

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High-voltage switchgear and controlgear

Part 200: AC metal-enclosed switchgear and controlgear for rated voltages above 1 kV and upto and including 52 kV

Switchgears are important nodal points in modern powerdistribution. Correspondingly important is their reliable functioning,a clearly defined switching behavior according to specifiedparameters as well as the protection of personnel and protectionagainst operational interruptions when an overload occurs.

The International Electrotechnical Commission (IEC) has taken upthe task of developing the required specifications, their worldwidestandardization and further development.

The same applies to IEC 62271-200 – the new standard formedium-voltage switchgear.

Retrospective

IEC 60298 – for four decades this abbreviation was the decisivefactor for the type testing of metal-enclosed switchgear. In themeantime there are tens of thousands of switchgear panels of theprimary and secondary distribution level based on this standardin use – certified according to the mandatory part of the standard and, if required, according to optional tests.

The passing of the following tests was obligatory in order to identify switchgear as type-tested:

Dielect ric test to verify the insulation level of the switchgear (tests with rated lightning impulse withstandvoltage and rated short-duration power frequency withstand voltage with the specifi ed values depending onthe respective rated voltage).

Temperature rise tests to verify the current carrying capacity with rated normal currents. Peak and short-time withstand current tests to verify the dynamic and thermal current carrying capacity of the main and earthcircuits; the tests are performed with rated peak short- circuit current or rated short- circuit making current orrated shorttime current or rated short- circuit breaking current.

Switching capacity test to verify the making/breaking capacity of the installed switchgear.

Mechanical funct ion test to verify the mechanical functions and interlocks.

Degree of protect ion tests to verify the protection against electric shock and foreign objects.

Pressure and st rength tests to verify the gas tightness and pressure resistance for gas- fi lled switchgear.

There is also the possibility of voluntarily certifying switchgear for resistance to internal arc faults and for personalprotection. Manufacturers and operators can select the criteria which are relevant to them from the following sixcriteria and have them tested.

Criterion 1: Doors and covers must not open.

Criterion 2: Parts of the switchgear must not fl y off.

Criterion 3: Holes must not develop in the external parts of the enclosure.

Criterion 4: Vertical indicators must not ignite.

Criterion 5: Horizontal indicators must not ignite.

Criterion 6: Earth connections must remain effective.

Siem ens HV Swi tchgear

In order to guarantee safe access to the individual switchgear components, e.g.the incoming cable, without isolatingthe busbar, the IEC 60298 standard differentiates between three types of compartmentalization that serve exclusivelyas protection against electric shock.

Metal-clad switchgear

Division of the switchgear panel into four compartments (busbar compartment, switching-device compartment,connection compartment and low-voltage compartment); partitions between the compartments made of sheet steel,front plate made of sheet steel or insulating material.

Compartmented switchgear

Division of the switchgear panel same as for metal- clad switchgear, but with the partitions between the individualcompartments made of insulating material.

Cubicle-type switchgear

All other types of construction that do not meet the above features of the metal- clad or compartmented designs.

In this context, access to the then common minimum-oil- content circuit- breakers for maintenance work without longeroperational interruptions was of prime importance because of the limited number of operating cycles. Therefore, withswitchgear in metalclad or compartmented design, the busbar in the busbar compartment and the incoming cable inthe connection compartment could remain in operation. With a cubicletype design, the incoming cable had to beisolated, but the busbar itself could remain in operation.

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Overview of IEC 62271-200

Although the old IEC 60298 standard was very helpful, in time it wassuperseded by the technological progress. Above all, the appearance ofmaintenance- free vacuum circuit- breakers, with operating cycles farexceeding the normal number, made frequent access to this circuit- breaker nolonger of prime importance.

The vacuum arc-quenching principle is technologically so superior to otherarc-quenching principles that the circuit- breaker can be fixed-mounted again.This resulted in the first- time use of gas insulation with the important features ofclimatic independence, compactness and maintenance- free design. However,both technologies – the vacuum arc-quenching principle and gas insulation –were not adequately taken into account in the existing standard. Therefore, atthe end of the nineties, the responsible IEC committees decided on thereformulation of the switchgear standard, which finally came into effect as IEC62271-200 in November 2003. At the same time the old IEC 60298 standardwas withdrawn without any transition period.

Four key features are of special note with the new IEC 62271-200 standard:

1. Changed dielectric requirements

According to IEC 60298, two disruptive discharges were permitted in a seriesof 15 voltage impulses for the test with rated lightning impulse withstandvoltage. According to the new standard, the series must be extended by another fi ve voltage impulses if adisruptive discharge has occurred during the fi rst 15 impulses. This can lead to a maximum of 25 voltage impulses,whereas the maximum number of permissible disruptive discharges is still two.

2. Increased demands on the circuit breaker and earthing switch

In contrast to the previous standard, the switching capacity test of both switching devices is no longer carried out asa pure device test. Instead, it is now mandatory to carry out the test in the corresponding switchgear panel. Theswitching capacity may get a negative infl uence from the different arrangement of the switchgear with contact arms,moving contacts, conductor bars, etc.

For this reason, the test duties T100s and T100a from the IEC 62271-100 standard are stipulated for the test of thecircuitbreaker inside the switchgear panel.

3. New partition classif ication

The new partition classes PM (partitions metallic = partitions and shutters made of metal) or PI (partitions nonmetallic= partitions and shutters made of insulating material) now apply with respect to the protection against electric shockduring access to the individual components.

The assignment is no longer according to the constructional description (metalclad, compartmented or cubicle- typedesign), but according to operator- related criteria.

4. Stricter internal arc classif ication

Significantly stricter changes have also been implemented here. The energy flow direction of the arc supply, themaximum number of permissible panels with the test in the end panel and the dependency of the ceiling height onthe respective panel height have been redefined.

In addition, the five following new criteria must always be completely fulfilled (no exceptions are permitted):

1. Covers and doors remain closed. Limited deformations are accepted.

2. No fragmentation of the enclosure, no projection of small parts above 60 g weight.

3. No holes in the accessible sides up to a height of 2 meters.

4. Horizontal and vertical indicators do not ignite due to the effect of hot gases.

5. The enclosure remains connected to its earthing parts.

For the internal arc classifi cation of substations with and without control aisle, the testing of the substation withinstalled switchgear is mandatory in the new IEC 62271-202 standard. The classification of the substation is onlyvalid in combination with the switchgear used for the test.

The classification cannot be transferred to a combination with another switchgear type as each switchgear behavesdifferently in the case of an internal arc (pressure relief equipment with different cross-sections and pickuppressures, different arcing conditions because of different conductor geometries).

SOURCE: Siemens AG – We are ready: IEC 62271-200