General information
On-load tap-changer devices of the RNOA type are designed for built-in step regulation under load of the voltage of general-purpose power transformers; they are manufactured for rated currents of 630; 800; 1250; 2000 A and rated voltage 35; 110; 220; 330 kV.
RNOA type on-load tap-changers are designed to operate in transformer oil at oil temperatures from +100°C to – 25°C, and also up to – 60°C without switching.
Climatic modifications U1, HL1 and T1.
Design
The on-load tap-changer device consists of the following assembly units: a switching mechanism, which includes a contactor hermetically separated from the transformer oil and a selector; angular and rotary gearboxes; connecting horizontal and vertical shafts; drive; temperature sensor-relay; a protective relay, as well as a position indicator and a transformer voltage regulator installed on the control panel.
The temperature sensor-relay interrupts the on-load tap-changer control circuit when the oil temperature is below –25°C.
The protective relay issues a signal to turn off the transformer if the on-load tap-changer contactor is not operating correctly.
The voltage regulator (automatic control unit) provides a command to turn on the on-load tap-changer. The voltage regulator operates automatically when the voltage at the transformer terminals changes.
The necessary technical characteristics (rated current, rated voltage, number of control stages, etc.) for a specific on-load tap-changer device are provided by the use of various types of contactor, selector and drive.
The on-load tap-changer devices are submersible by design. This means that the switching mechanism, which has a block design, is immersed in the transformer tank or a separate attached tank.
The devices allow remote control and manual control from the handle when setting up or testing the transformer.
Main parameters and technical characteristics of RNOA type on-load tap-changers
| Parameter name | Magnitude | |||
| Rated voltage, kV | 35, 110, 220, 330 | |||
| Rated current, A | 800 | 1250 | 1250 | 2000 |
| Stage voltage, kV | ||||
| Nominal | 3.1 | 3.0 | 3.4 | 3.0 |
| Maximum | 4.0 | 4.0 | 4.5 | |
| Number of control stages | ||||
| Short circuit test current, steady-state rms value, kA | 10.0 | 18.75 | 30.0 | |
| Mechanical wear resistance resource, not less than thousand switchings | 500 | |||
| Drive PDP-6U, PDP-6UA | ||||
| Switching time from one fixed position to another, s. | 3.8+20% | |||
General view and overall dimensions of a single-contact on-load tap-changer type RNOA
General view and overall dimensions of a two-contactor on-load tap-changer type RNOA
