3 Selecting transformers

3.1 Selecting transformer for option 1

For the scheme adopted power balance is maintained in the normal mode.

Consider the possible alarm modes:

a) for the T-1 is turned off in the winter after a maximum of T-2 will be transferred to the maximum capacity of 3.72 MW

b) when disconnecting the G-1, the winter maximum of T-1 and T-2 to supply the consumers of 10 kV will be transferred power:

c) disabling any of the units, for example G-3. In this case, the maximum load coil 110 T-3 will 8.96MVt.

Output mode most power generators.

At low loads during the summer load on the T-1 and T-2 is:

The total capacity of 56,133 MW transmitted. The power transmitted through the winding 35 kV transformer T-3 in the 110 kV network:

МWt;

In this mode, the loading coils 110 kV transformer

МWt;

Transformer T-1 and T-2 to the condition of the normal mode in Table 1:

In the transmit maximum power, taking into account 40% overload:

We accept the installation of the transformer type 2 TM-6300/110.

For this scheme the balance of power in normal mode are saved.

a) Let`s consider the possible emergence modes;

At turning off TR in summer maximum the generator G-1 and G-2 cover the load 18 MVA on 10 kv. The winding of 35 kV of each T-3 and T-4 will loaded by power of 6/2 = 3 MW;

b) At turning off G-1 in winter maximum through TR for supplying the consumers of 10 kV will transmit the power:

МWt;

The winding of 35 kV each of transformer T-3 and T-4 will load by power which is equal: 13.44/2 + 6/2 = 9.72 MW

As maximum power from all normal and emergency mode equal 4.56 MW, sequently:

We accept to installation the transformer of type TM – 32000/35 instead two transformers T1 and T2.

Power of transformers T-3 define from the condition of normal mode:

We accept the installation of the transformer type 2 TРНДС-25000/110.

3.2 Selecting transformer for option 2

Power transformers T-1 and T-2 for the normal mode is determined by the condition:

By the condition of emergency shutdown of T-1

By the condition of given maximum power:

Accept the installation of the two transformer-type TM 6300/110.

Power transformer T-3 is determined as for the first option. We accept to the installation the transformer type 2 ТРНДС – 25000/110.

4 Calculation of annual energy losses in transformers

4.1 Calculation of option 1

Continuation of loads: winter – 200 (Dz), summer – 165 (Ds).

Transformer types ТРДНС-32000/35. Their characteristics needed for calculation of the year losses – , ,

Year losses of energy in steel:

Year losses of energy in copper:

_{Transformer type} ТДТН-25000/110. Their characteristics needed for calculation of the year losses – , ,

_{Year losses of energy in steel}:

_Year losses of energy in copper in three-winding transformer defines as for each winding LV, НV, AV corresponding with their loads.

_{If in the catalogs for three-winding transformers there are losses of the short-circuit of the pair of HV and CH windings Pkz. BH-CH, then at the power of each winding equal to 100%. The total loss of individual windings is equal to:}

.