Short-circuit tests power circuits

Figure 13.23 Oscillograms of an actual short-circuit test carried out on a power distribution panel (Courtesy ECS)...

For more clarity we have reproduced in Figure 14.3 an actual test circuit and in Figure 14.4, the oscillograms of the test results of a short-circuit test successfully carried out on an LT power distribution panel (Figure 14.8) for a system fault level of 50 kAfor 1 second, at CPRI (Central Power Research Institute). From a study of these oscillograms (Figure 14.4), we can infer the following test results ... 

The short-circuit test is conducted by shorting one of the transformer s cods, and applying rated current to the other cod. Only a fraction of the rated voltage is needed to produce the rated current. The input current and power are then measured. Figure 10.10 shows a circuit diagram for this test. 

Figure 14.3 General arrangement of a power circuit to conduct a short-circuit test...

Figure I. Results of an 8-month outdoors test of PEC containing a 0.8-cm2 thin film, painted CdSe photoelectrode (not photoetched), CoS counterelectrode, and 7M KOH, 2M S, 7M S, ImM Se solution. (OCV) open-circuit voltage (SCC) short-circuit current (EFF) solar conversion efficiency ( AMI.5). Between measurements the cell operated on maximum power (68 fi load). No appreciable change in fill-factor occurred during the test.

The waveguide system used to measure the dielectric parameters of water and other lossy liquids has been described previously (3J. Basically it involves the measurement of the power profile of a wave reflected from a movable short circuit as it traverses the liquid under test. 

Application of a three-phase short circuit to the terminals of an unloaded induction motor is not a practical factory test, especially for a large high-voltage motor, because the motor can only be excited at its stator windings from the power supply. A three-phase short circuit at or near the stator terminals can occur in practice e.g. damaged supply cable, damage in the cable terminal box. The parameters of the stator and rotor windings can be obtained from other factory tests. However, the derived reactance can be defined in the same manner as those for the synchronous machine, but with... 

Prototype Efficiency Measurements. A variety of LSC devices have been tested by ourselves and others. Table I is Intended to be a representative list of typical performance parameters. Again, the geometric gain is the ratio of the area exposed to the sun to the active area of the edge. The flux gain is the factor by which the short circuit current increased when attached to the plate, as opposed to facing the sun directly. The cell efficiency is the measured or assumed AMI efficiency of the solar cells used (which in all cased were silicon). The collector efficiency is the total electrical power out divided by the total sunlight power incident on the plate. 

The battery development process included a large number of cell tests. For instance, in order to characterize the cells, the usable power was measured over SOC and temperature. Furthermore, early in the process, cell abuse tests were performed to qualiiy their usage in a vehicle production program. Such abuse tests included overcharge, overdischarge, short-circuit, nail-penetration, hot-box and crush procedures. 

Analog in-circuit test addresses testing for shorts in the printed wire circuitry analog components, passive devices such as resistors, inductors, and capacitors and simple semiconductor components such as diodes and transistors. Analog in-circuit testing is conducted without applying power to a board that is, it is an unpowered test methodology. 

Loop impedance tests are carried out to determine the loop impedance between the power source(s) and the point in the installation where the test is done. The device employed measures the current which passes through a resistor and displays the result in ohms. It is used to determine the loop impedance between phases, phase to neutral or any phase to earth. Some instruments incorporate a transformer to enable the neutral/earth loop impedance to be measured. From Ohm s law these readings can then be expressed in prospective short circuit fault currents. 

Saft [41,42] has reported favorable abuse test results for their high power IJNiCoMiMsO grafdute cells. NGK [43] has already reported favorable test results for their 95 Wh (25 Ah) Uthium-ion cells LiMn204/hard carbon cells (naU, external short circuit, over-charge, and heating tests). The NGK ceU includes... 

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