In many engineering situations it is useful to scale, or normalize, dimensioned quantities. This is commonly done in power system analysis. The standard method used is referred to as the per-unit system. Historically, this was done to simplify numerical calculations that were made by hand. Although this advantage is eliminated
Year: 2015
The heart of any power electronic circuit is its semiconductor-switching network. The question arises here as to whether we have to use switches to perform electrical power conversion from the source to the load. The answer, of course, is no, as there are many circuits that can perform energy conversion
There are four ways to solve power quality problems: 1- Design equipment and electrical systems to prevent electrical disturbances from causing equipment or systems to malfunction. Where, manufactures of sensitive equipment can reduce or eliminate the effect of power quality problems by designing their equipment to be less sensitive to
IEEE defined power quality disturbances into seven categories based on wave shape: 1. Transients 2. Interruptions 3. Sag/ Under voltage 4. Swell/ Overvoltage 5. Waveform distortion 6. Voltage fluctuations 7. Frequency variations 1. TRANSIENTS Potentially the most damaging type of power disturbance, transients fall into two subcategories: 1. Impulsive 2.
A null method of measurement is a simple, accurate and widely used method which depends on an instrument reading being adjusted to read zero current only. The method assumes: (i) If there is any deflection at all, then some current is flowing; (ii) If there is no deflection, then no
All analogue electrical indicating instruments require three essential devices: (A) A DEFLECTING OR OPERATING DEVICE: A mechanical force is produced by the current or voltage which causes the pointer to deflect from its zero position. (B) A CONTROLLING DEVICE: The controlling force acts in opposition to the deflecting force and
There are several important reasons why a grounding system should be installed. But the most important reason is to protect people! Secondary reasons include protection of structures and equipment from unintentional contact with energized electrical lines. The grounding system must ensure maximum safety from electrical system faults and lightning. A
There are several ways in which the system and the generator may interact with subsynchronous effects. A few of these interactions are basic in concept and have been given special names. We mention three of these that are of particular interest: Induction generator effect Torsional interaction Transient torque Each of
Subsynchronous resonance is a condition that can exist on a power system where the network has natural frequencies that fall below the fundamental frequency of the generated voltages. Transient currents flowing in the ac network have two components; one component at the frequency of the driving voltages and another component
Many adjustable-speed drives are equally sensitive to voltage sags as process control equipment discussed in the previous section. Tripping of adjustable-speed drives can occur due to several phenomena: • The drive controller or protection will detect the sudden change in operating conditions and trip the drive to prevent damage to
