Question

Electrical power:

Please do a Short answers for all of these questions.... thanks :

3. What device on the California-Oregon-Intertie has been constructed to minimize the risk of the power system slipping a pole in the case of a loss of downstream transmission capacity.

4. In an extra-high voltage transmission system, describe what determines the direction of real power flow (megawatts).

5. In an extra-high voltage transmission system, given a power angle of less than 15 degrees and normal system conditions, describe what determines the direction of reactive power flow (megavolts-amperes-reactive).

Answer 1

3. The device is known as STATIC VAR COMPENSATOR (SVC), the reactive power devices that generate or absorb reactive power as required by the electric power system, i.e., Pacific Intertie. It reduces the risk of the power system slipping a pole in the case of a loss of downstream transmission capacity.

4. The Poynting Vector determines the direction of real power flow. When power is consumed, the voltage and current rises and fall together (with some variation due to power factor). As you consume energy from the AC grid the voltage generally stays the same but the current rises and falls depending on your consumption. As you reduce your demand to zero, the current falls to zero, then when you start feeding into the AC grid, the current becomes negative with respect to voltage (ie., 180 degrees out of phase). So to determine energy flow or power flow (real power or reactive power) , you need to know the current in the wire and whether that current is negative or positive with respect to the voltage. You can do this by measuring the voltage and current at the same time (instantaneous values), then multiply them together, if the answer is negative, you are feeding into the grid, if it's positive, you are using power.

5. Reactive power flow direction depends on the excitation of the generator and/or type of load. If load is operating at lagging power factor then reactive power will flow from generator to load. If load is operating at leading power factor then reactive power will flow from load to generator. If load is operating at unity power factor then no reactive power will flow. As power angle (θ) is less than 15 degrees which means it's a leading power factor.