English Original Reader for Technical Students. Power transformers: short-circuit testing, monitoring systems (Smart Grid) - страница 3

Scheme of using IMS for the control of transformer’s winding state avoiding disconnecting from the network is depicted in Figure 1 [by 1–4].

Figure 1. Information-measuring system for control of transformer’s windings state in service.

The algorithm of IMS’s work is the following. The continuous control of the winding’s state of the controlled power transformer is ensured by a constant monitoring of deviation of inductance value from the base value of inductance, which is obtained from the block of the base inductance.

During the work of the three-phase controlled power transformer (T) for the three-phase resistive load (Load) the value of primary voltage U1 is obtained by measuring converters primary voltage (high-voltage transformers TV1).

Signal from the converters was input to the entrance of the block which brings the primary voltage to the second one. In this block the value of the primary voltage, which is corrected to the second, is calculated:

Signal from the converters was entered to the entrance of the block of bringing the primary voltage to the second. In this block the value of the primary voltage, which is corrected to the second, is calculated:

where: Kt is the known given value of the transformation ratio of the power transformer.

Signals from the measuring converters of second voltage (voltage transformers TV2) and signals from the output of the previous block are input to the entrance.

In the block of calculation of voltage difference, which is corrected to the second side, we determine

where: U2 is the value of second voltage, measured by converters TV2.

The calculations are performed in the assigned time interval in the block of calculation of voltage’s average value:

where: uj is the difference between corrected to the second side voltages on the transformer;

t1 and t2 are the temporary boundaries of the partition interval.

In the block of calculation of the current derivation the increase of the current in the assigned time interval is calculated:

Here ij is the value of current in the secondary winding of the controlled transformer, measured by current converters (current transformers CT).

In the block of calculation of inductance, the instantaneous value of inductance is determined in the assigned time interval: