GAS INSULATED SUBSTATION DEFINITIONS AND BASICS
DEFINITIONS
This course is based on terms used in IEEE and IEC regulations. Several crucial terms
are for better understanding of the presented material.
GIS - There are two terms presented in IEC “Gas Insulated Switchgear” and IEEE
“Gas Insulated Substations.”In IEEE C37.122 - Gas insulated switchgear (GIS): a compact, multicomponent device, enclosed in a grounded metallic case in which the basic insulating medium is
SF6 gas and which typically includes buses, switches, circuit breakers, and other related devices.
In IEC 62271-203 - Metal-enclosed switchgear and control gear: switchgear and control gear devices with an external metal case were planned to be grounded, and complete except for external connections. There is no precise definition of GIS. Metal-Enclosed Switchgear and Control gear - Switchgear and control gear devices with an external metal case were planned to be grounded and complete except for
external connections, as described in IEC 62271-203.
Gas Insulated Metal-Enclosed Switchgear - Metal- enwrapped switchgear in which the
insulation is received, at least partially, by an insulating gas other than air at atmospheric pressure, as described in IEC 62271-203. This definition typically relates to high voltage switchgear and control gear. Three-phase enwrapped gas isolated
switchgear applies to switchgear with the three phases enwrapped in a common case.
Single-phase enwrapped gas insulated switchgear relates to switchgear with each phase closed in a single independent case.
Gas Insulated Switchgear Enclosure - Part of the gas-isolated metal- enwrapped switchgear holding the isolating gas under the dictated conditions essential to keep the greatest isolation level safely, guarding the device against external impacts and
giving a high degree of protection to staff, as described in IEC 62271-203. In IEEE
C37-122, earthed element of the gas isolated metal-enclosed switchgear device holding the isolating gas under the dictated conditions essential to keep the needed isolation level, guarding the device against external impacts and giving a high degree
of protection from an approach to live energized parts.
GIS Compartment - A part of a gas isolated switchgear assembly that is closed except
for gaps needed for interconnection gives isolating gas separation from other
compartments. A space may be assigned by the main elements in it, for example,
circuit breaker space, disconnect switch space, bus space, and so on, as described in
IEEE C37.122. A space of GIS as described in IEC 62271-203 as part of a gas isolated
metal-cased switchgear, is completely closed except for gaps needed for interconnection and control. A space may be assigned by the main element held therein, for example, circuit breaker space or bus bar space.
Design Pressure of Enclosures - The greatest gas pressure to which a gas isolated
switchgear case will be subjected under normal service operation, including the
heating impacts of rated continuous current, as described in IEEE C37.122.
Gas Monitoring Systems - Any devices for measuring, signalizing, or providing remote
warning of the condition or change in condition of the gas in the case, such as
pressure, density, moisture level, and so on, as described in IEEE C37.122.
Gas Leakage Rate (Absolute) - The quantity of gas getting away by a time unit showed
in units of Pa m3/s, as described in IEEE C37.122.
Gas Leakage Rate (Relative) - The absolute leakage rate associated to the total
quantity (mass or volume) of gas in each space at the rated filling pressure (or density).
It is defined in percentage per year, as described in IEEE C37.122.
Gas Pass Through Insulator - An internal insulator backing one or more conductors
specifically made to provide the passage of gas between adjoining spaces, as
described in IEEE C37.122.
Gas Zone - A part of the GIS that may be comprised of one or several gas spaces that have a common gas monitoring system. The case can be single-phase or three-phase,
as described in IEEE C37.122.
Local Control Cubicle (or Cabinet) (LCC) - A cubicle or cabinet usually holding
secondary devices including control and interlocking, measuring, indicating, alarm,
annunciation, and mimic one-line diagrams related with the primary devices. It may
also let in protective relays if defined by the user.
Support Insulator - An internal isolator backing one or more conductors, as described
in IEC 62271-203.
Partition - Part of an assembly distinguishing one space from other spaces. It gives
gas isolation and backing for the conductor (gas barrier isolator), as described in
C37.122. A space as described in IEC 62271-203, which is a backing isolator of gas
isolated metal enclosed switchgear distinguishing one space from other spaces.
Design Pressure of Cases - Relative pressure utilized to find out the design of the
case. It is at least same to the maximum pressure in the case at the greatest
temperature that the gas used for insulation can reach under defined maximum service
circumstances. The transient pressure happening during and after a breaking
procedure (e.g., a circuit breaker) is not to be studied in the decision of the design
pressure, as described in IEC 62271-203.
Relative Pressure across the Partition - Relative pressure across the partition is at
least same to the greatest relative pressure across the space during maintenance
actions. The transient pressure happening during and after a breaking procedure (e.g.,
a circuit breaker) is not to be studied in the decision of the design pressure, as
described in IEC 62271-203.
Operating Pressure of Pressure Relief Element - Relative pressure selected for the
opening procedure of pressure relief elements, as described in IEC 62271-203.
Routine Test Pressure of Cases and Partitions - Relative pressure to which all cases
and partitions are submitted after production, as described in IEC 62271-203.
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