Gas Insulated Substations. Группа авторов

Чтение книги онлайн.

СКАЧАТЬ × × 550 710 1175 1550 × × 550 740 1175 1550 × × 800 960 1425 2100 × × 1100 1100 1800 2400

      1.4.4 Rated Power Frequency

      Most power frequencies for GIS are 50 Hz originated in Europe and 60 Hz originated in North America. Apart from 16 ⅓ Hz and 25 Hz for railroad applications, the majority of GIS applications are with 50 and 60 Hz. These two frequencies are distributed world‐wide and form regions and countries with one or the other frequency. Some countries, for example, Japan and Saudi Arabia, have both frequencies.

      The dielectric impact to the GIS design of these frequencies is negligibly low. The thermal impact needs to be considered when the current rating is approaching the limits, because at 60 Hz the power density is higher leading to higher thermal rise. Temperature limits should not be exceeded because of possible damage to insulators or contact systems.

      1.4.5 Rated Continuous Current

      The continuous current rating is a basic design criterion of GIS for bus and contact sizing. The complex structure of GIS allows close influence of the different devices such as circuit breakers, ground switches, disconnect switches, current transformers, voltage transformers, and bus bars in terms of heat dissipation and temperature rise. For this reason, the IEEE and IEC standards require temperature rise tests to confirm the correct function of all devices included in GIS. A so‐called typical bay configuration will be used for this test.

One of the factors specific to a GIS installation may show that the rated continuous current may be different for the bus bar or the feeders depending on the substations’ scheme. Typical rated continuous currents are shown in Table 1.6.

      1.4.6 Rated Short Time Withstand Current

The rated short time withstand current (I _K), the peak‐withstand current (I _p), and the duration of the short circuit (t _K) are basic dimensioning parameters for GIS design (see Table 1.7).

These values have a great impact on the electromechanical forces to the insulators and conductors, and on the thermal rise, mainly of the contact system. These values are also tested by specific type tests to confirm the satisfactory function of the different devices of a GIS, such as the circuit breaker, disconnect, ground switch, and bus bars.

Table 1.6 Typical current ratings of GIS related to voltage classes

5000–8000 A				×	×	×
4000–5000 A				×	×	×
3150–4000 A			×	×	×
2500–3150 A	×	×	×	×
1250–2500 A	×	×
	52–72.5 kV	100–170 kV	245–300 kV	362–550 kV	800 kV	1100 kV

Table 1.7 Typical short‐circuit current ratings of GIS related to voltage classes

63–100 kA				×	×	×
50–63 kA		×	×	×	×	×
31.5–50 kA		×	×	×
25–31.5 kA		×	×
16–25 kA	×
	52–72.5 kV	100–170 kV	245–300 kV	362–550 СКАЧАТЬ В начало < 25 26 27 28 29 30 31 > В конец