2) According to the number of phases: single-phase and three-phase.
3) According to the transformation principle, it can be divided into electromagnetic voltage transformer (VT) and capacitive voltage transformer (CVT).
4) According to the number of windings: a double-winding voltage transformer with only one secondary winding on the low-voltage side; Three-winding voltage transformer with two independent secondary windings; Four-winding voltage transformer with three independent secondary windings.
5) According to the grounding state of the primary winding: grounding voltage transformer, single-phase voltage transformer with one end of the primary winding directly grounded, or three-phase voltage transformer with the star connection point (neutral point) of the primary winding directly grounded; Ungrounded voltage transformer, all components of the primary winding, including terminals, are voltage transformers insulated to the ground according to the rated insulation level.
6) According to the equipment type: indoor and outdoor.
7) According to the structural form, it can be divided into single-stage voltage transformers, voltage transformers with primary and secondary windings on the same stem and non-graded insulation; In the cascade voltage transformer, the primary winding is composed of several multistage windings with the same number of turns and the same geometric size in series, and the secondary winding and the grounding terminal of the primary winding are on the same stem.
8) According to insulation medium: drying, pouring, oil immersion, gas insulation, etc!
The main functions are as follows:
1. Provide necessary signals for reclosing. The way of two-point line closing is to check whether there is no voltage or the same period. Line PT can provide voltage signal for reclosing.
2. Capacitive voltage transformers used in some lines PT can provide signal channels for carrier communication.
3. At present, metering voltage is provided for some special power supply user lines.
capacitor voltage transformer
1, overview
Capacitive voltage transformer, 1970 developed the first domestic 330 kV CVT, 1980 and 1985 developed the first and second generation 500 kV CVT, 1990 and 1995 developed the third and fourth generation 500 CVT. The main features of CVT are:
-High electrical strength, large insulation margin and reliable operation.
-It can reliably suppress ferroresonance. The successful adoption of the new synthesis period and strict quality control ensure that each CVT can effectively damp the ferromagnetic resonance of various frequencies at any voltage from low to high.
-Excellent response characteristics. After short circuit, the secondary residual voltage can be reduced to less than 5% within 20MS, which is especially suitable for fast relay protection.
-Patented technology for harmonic monitoring of power grid.
2. Application
Capacitive voltage sensor can be used for voltage and power measurement, energy metering, relay protection, automatic control, etc. in high-voltage and ultra-high-voltage power systems, and can also be used as a coupling capacitor in power line carrier communication systems. If necessary, internal accessories and external terminals for harmonic voltage measurement can be provided.
(1) Installation and operation place: outdoor or indoor.
(2) Altitude: the products of 330 kV and below shall not exceed 2000m ... the products of 500kv shall not exceed 1000m, and plateau products up to 4000m can be provided according to the ordering requirements.
(3) Ambient temperature: -40/+40 degrees, -25/+45 degrees. It is selected by the user when ordering (other temperature categories can also be selected).
(4) Wind speed: no more than 42m/s.
(5) Pollution grade: Grade I pollution (creepage specific distance of external insulation ≥17 mm/kv); Ⅲ pollution (creepage specific distance of external insulation ≥ 25mm/kV); Ⅳ Pollution (creepage specific distance of external insulation)
≥3 1 mm/kv). The pollution level is selected by the user when ordering.
(6) Re-icing thickness: no more than10mm. ..
(7) Earthquake intensity: no more than 8 degrees. According to the requirements of users, we can also provide products with higher earthquake resistance.
(8) Rated frequency of the system: 50Hz or 60Hz. Confirm that there is a user order.
(9) System grounding conditions: neutral point is effectively grounded or neutral point is not effectively grounded; Determined by the user when ordering.
Respondent: aoaoo