IEC 62271-200 defines four categories of Loss of Service Continuity: LSC1, LSC2, LSC2A, LSC2B. LSC1 functional unit = Functional unit having one or several high-voltage accessible compartments, such that, when any of these accessible high-voltage compartments is open, the busbar and one or several other functional units of the switchgear must be de-energized LSC2 functional unit = Functional unit having at least an accessible compartment for the high-voltage connection (called connection compartment), such that, when this compartment is open the busbar can remain energized. All the other functional units of the switchgear can continue to be operated normally. Note: When LSC2 functional units have accessible compartments other than the connection compartment, further subdivisions into LSC2A and LSC2B are defined. LSC2A functional unit = Functional unit having several high-voltage accessible compartments, such that, the busbar can remain energized when any other accessible high voltage compartment is open. All the other functional units of the switchgear can continue to be operated normally LSC2B functional unit = Functional unit having several high-voltage accessible compartments, such that, the high-voltage connections compartment and the busbar can remain energized when any other accessible high voltage compartment is open. All the other functional units of the switchgear can continue to be operated normally. Unidad funcional LSC2A = Unidad funcional que tiene varios compartimentos accesibles de alto voltaje, de manera que, la barra colectora puede permanecer energizada cuando cualquier otro compartimiento de alto voltaje accesible está abierto. Todas las demás unidades funcionales del equipo de distribución pueden continuar funcionando normalmente 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 individual compartments 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 circuitbreakers for maintenance work without longer operational interruptions was of prime importance because of the limited number of operating cycles. Therefore, with switchgear in metalclad or compartmented design, the busbar in the busbar compartment and the incoming cable in the connection compartment could remain in operation. With a cubicletype design, the incoming cable had to be isolated, but the busbar itself could remain in operation. Overview of IEC 62271-200 Siemens HV Switchgear Although the old IEC 60298 standard was very helpful, in time it was superseded by the technological progress. Above all, the appearance of maintenance- free vacuum circuit-breakers, with operating cycles far exceeding the normal number, made frequent access to this circuit-breaker no longer of prime importance. The vacuum arc-quenching principle is technologically so superior to other arc-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 of climatic 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, at the end of the nineties, the responsible IEC committees decided on the reformulation of the switchgear standard, which finally came into effect as IEC 62271-200 in November 2003. At the same time the old IEC 60298 standard was 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 series of 15 voltage impulses for the test with rated lightning impulse withstand voltage. According to the new standard, the series must be extended by another fi ve voltage impulses if a disruptive 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 as a pure device test. Instead, it is now mandatory to carry out the test in the corresponding switchgear panel. The switching 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 the circuitbreaker inside the switchgear panel. 3. New partition classification 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 shock during access to the individual components. The assignment is no longer according to the constructional description (metalclad, compartmented or cubicle-type design), but according to operator-related criteria. 4. Stricter internal arc classification Significantly stricter changes have also been implemented here. The energy flow direction of the arc supply, the maximum number of permissible panels with the test in the end panel and the dependency of the ceiling height on the 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 with installed switchgear is mandatory in the new IEC 62271-202 standard. The classification of the substation is only valid in combination with the switchgear used for the test. The classification cannot be transferred to a combination with another switchgear type as each switchgear behaves differently in the case of an internal arc (pressure relief equipment with different cross-sections and pickup pressures, different arcing conditions because of different conductor geometries). PAGE 10 Coast stop is precisely as it sounds - the drive output is de-energized and the motor spins down at whatever speed the load imparts on it. This is typically the “emergency stop” mode dictated by the U.S. National Electric Code
