1) A symmetrical short circuit occurs on a 22kV bus bar. The fault apparent power is 73MVA and the fault current is 1.91kA.
2) Fault current measurements for a 50MVA alternator allow calculation of its per unit sequence reactances as 1.403, 0.351, and 0.151.
3) For a 100MVA generator with given reactances, the sustained short circuit current is 2467A, initial breaker current is 16882A, and maximum DC current is not provided.
To understand the basic working principle of a transformer.
To obtain the equivalent circuit parameters from Open circuit and Short circuit tests, and to estimate efficiency & regulation at various loads.
There are numerous systems in use today that convert the fixed
voltage and fixed frequency a.c. supply into variable voltage or /and variable frequency supply using power semiconductor devices. The simplest forms of ac-to-ac converters are the a.c. voltage controllers that
convert fixed voltage fixed frequency into variable voltage fixed frequency. These voltage controllers are also called a.c. choppers or a.c. voltage regulators. Some of the applications are motor drive systems; electric furnaces heat control, light dimmers, HVAC systems, welding and other industrial applications. This chapter discusses the single phase and three-phase a.c. voltage controller (a.c. choppers) and their performance with resistive and resistive-inductive loads.
The ac-to-ac power converters available in industry today do not actually convert power directly from a.c. power of one frequency to a.c. power of another frequency. Instead, these converters first convert
electrical power to d.c. using a rectifier, and then convert power back into a.c. using an inverter.These are called two-stage converters. However,
a cycloconverter is a frequency changer that converts an a.c. supply of fixed input frequency directly to an a.c. output of another frequency.
Cycloconverters not only eliminate the problem of having multiple systems to perform a single function, they also limit the flow of power to a single switch at any one period in time. Therefore, there is no bus link,
d.c. or otherwise, included in a cycloconverter topology between power input and power output.
HVDC Bridge and Station Configurations
1. General HVDC – HVAC Comparisons
2. Components of a Converter Bridge
3. HVDC scheme configurations
Operation of the HVDC converter
1. General assumptions
2. Rectifier operation with uncontrolled valves and X = 0
3. Rectifier operation with controlled valves and X = 0
4. Rectifier operation with controlled valves and X 0
5. Inverter operation with controlled valves and X 0
6. Commutation and Commutation Failure
7. Reactive Power Requirements
8. Short-circuit capacity requirements for an HVDC terminal.
9. Harmonics and filtering on the AC and DC sides
ENHANCEMENT OF ACTIVE POWER FLOW CAPACITY OF A TRANSMISSION LINE USING MSC‐TC...ijiert bestjournal
This paper represents the MSC-TCR scheme of shun t compensation used in FACTS. The laboratory setup of the SVC circuit using a Thyristor controlled reactor in parallel with mechanically switched capacitor will discussed in this paper. Results from the lab setup to exhibit firing angle adjustment to inject or absorb VAr into the system will also be described. During the process,losses happened are also discussed.
1. Unit IV Practice Questions
Q1. A symmetrical short circuit occurs on the 22KV load bus bar. Find the fault apparent power and the
fault current. Choose a base of 150MVA. Also draw the reactance diagram
[1.91KA, 73MVA]
Q2. A 50 MVA, 11KV, 3 phase alternator was subjected to different types of faults. The fault currents
were: 3 phase fault 1870A,LL fault 2590A and SLG fault 4130A. The alternator is solidly grounded. Find
the per unit values of the 3 phase sequence reactances. [1.403, 0.351, 0.151]
Q3. A generator connected through a 5 cycle circuit breaker to a transformer, is rated 100MVA, 18KV
with 19%, 26% and 130% as sub- transient, transient and steady state reactances respectively. It is
operating under no load and rated voltage when a three phase short circuit occurs between the breaker
and transformer. Find:
(i) The sustained short circuit current [2467]
(ii) The initial rms current in the breaker [16882]
(iii) The maximum possible DC component of the short circuit current in the breaker
Q4.
A 3 phase fault occurs at
point F. The reactances
are marked in per unit
values based on 100MVA.
Neglecting the pre fault
power and losses,
calculate the fault MVA at
F. Allow a multiplying
factor of 1.4.
[1430, 2000]