High voltage switchgear

From Wikipedia, the free encyclopedia

According to IEC, high voltage switchgear is any switchgear and switchgear assembly of rated voltage higher than 1000 volts.

high voltage switchgear is any switchgear used to connect or to disconnect a part of a high voltage power system.

These switchgear are essential elements for the protection and for a safety operating mode without interruption of a high voltage power system. This type of equipment is really important because it is directly linked to the quality of the electricity supply.

The high voltage is a voltage above 1000 V for alternating current and above 1500 V for direct current.

The high voltage switchgear was invented at the end of the 19th century for operating the motors and others electric machines[1]. It has been improved and it can be used in the whole range of high voltage until 1100 kV[2].


Disjoncteurs 245 kV dans un poste AIS
Poste blindé (GIS) 420 kV
Appareillage compact (hybride) 145 kV 40 kA en Australie
245 kV Circuit breaker in air insulated substation 420 kV Gas insulated switchgear 145 kV 40 kA Compact switchgear assembly

Contents

[edit] Classification

[edit] Functional Classification

[edit] Disconnectors and earthing switches

They are above all safety devices used to open or to close a circuit when there is no current through them. They are used to isolate a part of a circuit, a machine, a part of an overhead-line or an underground line for the operating staff to access it without any danger.

The opening of the line isolator or busbar section isolator is necessary for the safety but it is not enough. Grounding must be done at the upstream sector and the downstream sector on the device which they want to intervene thanks to the earthing switches.

In principle, disconnecting switches do not have to interrupt currents, but some of them can interrupt currents (up to 1600 A under 10 to 300V) and some earthing switches must interrupt induced currents which are generated in a non-current-carrying line by inductive and capacitive coupling with nearby lines (up to 160 A under 20 kV) )[3].

[edit] High-current switching mechanism

They can open or close a circuit in normal load. Some of them can be used as a disconnecting switch. But if they can create a short-circuit current, they can not interrupt it[4], [5].

[edit] Contactor

Their functions are similar to the high-current switching mechanism, but they can be used at higher rates. They have a high electrical endurance and a high mechanical endurance[6].

Contactors are used to frequently operate device like electric furnaces, high voltage motors. They can not be used as a disconnecting switch.

They are used only in the band 30 kV to 100 kV.

[edit] Fuses

The fuses can interrupt automatically a circuit with an overcurrent flowing in it for a fixed time. The current interrupting is got by the fusion of an electrical conductor which is graded.

They are mainly used ot protect against the short-circuits. They limit the peak value of the fault current.

In three-phase electric power, they only eliminate the phases where the fault current is flowing, which is a risk for the devices and the people. Against this trouble, the fuses can be associated with high-current switches or contactors.

They are used only in the band 30 kV to 100 kV.

[edit] Circuit Breaker

A high voltage circuit breaker is capable of making, carrying and breaking currents under the rated voltage (the maximal voltage of the power system which it is protecting) : Under normal circuit conditions, for example to connect or disconnect a line in a power system; Under specified abnormal circuit conditions especially to eliminate a short circuit. From its characteristics, a circuit breaker is the protection device essential for a high voltage power system, because it is the only one able to interrupt a short circuit current and so to avoid the others devices to be damaged by this short circuit. The international standard IEC 62271-100 defines the demands linked to the characteristics of a high voltage circuit breaker[7].

The circuit breaker can be equipped with electronic devices in order to know at any moment their states (wear, gaz pressure…) and possibly to detect faults from characteristics derivatives and it can permit to plan maintenance operations and to avoid failures[8], [9].

To operate on long lines, the circuit breakers are equipped with a closing resistor to limit the overvoltages [10], [11].

They can be equipped with devices to synchronize the closing and/or the opening to limit the overvoltages and the inrush currents from the lines, the unloaded transformers, the shunt reactances and the capacitor banks [12], [13].

Some devices are designed to have the characteristics of the circuit breaker and the disconnector[14]. But their use is limited.


[edit] See also

[edit] References

  1. ^ (English)British Pattern GB 20069 Improvements in Apparatus for Controlling the Application or Use of Electric Currents of High Tension and Great Quantity in 1893, on espacenet.com
  2. ^ (English) Lin Jiming et al., Transient characteristics of 1 100 kV circuit-breakers, International Symposium on International Standards for Ultra High Voltage, Beijing, Juillet 2007.
  3. ^ (French)IEC 62271-102 for A.C. disconnectors and earthing switches
  4. ^ (French)Norme CEI 60265-1 Interrupteurs pour tension assignée supérieure à 1 kV et inférieure à 52 kV
  5. ^ (French)Norme CEI 60265-2 Interrupteurs pour tension assignée supérieure à 52 kV
  6. ^ (French)Norme CEI 60470 Contacteurs pour courant alternatif haute tension et démarreurs de moteurs à contacteurs
  7. ^ (French)Norme CEI 62271-100 Disjoncteurs à haute tension
  8. ^ (French)E.Thuries, G.Ebersohl, J.P.Dupraz, O.Chetay, J.P.Montcorgé, Introduction de l'électronique numérique dans les auxiliaires de l'appareillage et amélioration de la fiabilité, 1994, CIGRE session 1994, rapport 23/13-09
  9. ^ (French)Denis Dufournet, Disjoncteurs SF6 - Évolution de 1959 à 1994, 1994, Revue générale de l'électricité n° 5
  10. ^ (English) D.E. Heldman, I.B. Johnson, C.H. Titus, D.D. Wilson, Switching of Extra-High-Voltage Circuits, Surge reduction with circuit-breaker resistors, 1964, IEEE Transactions on Power Apparatus and Systems, Vol. 83 (1964-12)
  11. ^ (French)Eugène Maury, Problèmes apparaissant aux tensions les plus élevées lors de la manœuvre des disjoncteurs, 1964, CIGRE session 1964
  12. ^ (French)Eugène Maury, La fermeture synchronisée des disjoncteurs 525 kV et 765 kV, moyen de réduire les surtensions de manœuvre sur lignes à vide, 1966, CIGRE session 1966.
  13. ^ (English) Groupe de travail CIGRE 13.07, Controlled switching of HV AC circuit breakers, 1999, Electra N° 183
  14. ^ (French)Norme CEI 62271-108 Disjoncteur-sectionneurs

[edit] External links