[Electric engineering.] . round occurs at G on line i?, lamp /3will go out and /1? /2 willbrighten up, but willnot come up to fullcandlepower becausetwo of them will be inseries between B and there is a groundat G on line A,all the lamps will comeup to full candlepower, because they will all get the fullvoltage, 73 being across A B and /,, /2 in series across A is thus seen that a ground on any one of the three linesaffects the lamps differently, so that by noting their per-formance, the line on which there is a ground may be located. K W Ground Q a Fig. 3? 30. The ground detectors j
[Electric engineering.] . round occurs at G on line i?, lamp /3will go out and /1? /2 willbrighten up, but willnot come up to fullcandlepower becausetwo of them will be inseries between B and there is a groundat G on line A,all the lamps will comeup to full candlepower, because they will all get the fullvoltage, 73 being across A B and /,, /2 in series across A is thus seen that a ground on any one of the three linesaffects the lamps differently, so that by noting their per-formance, the line on which there is a ground may be located. K W Ground Q a Fig. 3? 30. The ground detectors just described apply moreparticularly to low-tension direct-current installations, butsimilar arrange-ments maybe usedon alternating-cur-rent systems byusing potentialtransformers. shows the meth-od used by theWesting ho useCompany on someof their alterna-ting-currentswitchboards. Theregular voltmeterV, with which the switchboard is equipped, is here used alsoas a ground detector. Pis a plug switch by means of which. Fig. 38. §17 ELECTRIC LIGHTING. 37 points 1 and 2 or 1 and 3 may be connected together. Underordinary conditions, the plug is in 1 and 2, thus connectingthe primary of the potential transformer across the line,and V serves as an ordinary voltmeter. 5 is a key, orpush button, that, when pressed, connects one side of theline to ground through the transformer primary. If therehappens to be a ground on the side b, as shown at G, thevoltmeter will give a reading, and the attendant can judgeby the size of the deflection as to whether the ground is aserious one or not. The path of the current is b—G—G—5—toprimary-i-~-tf. By placing the plug in points 1 and S,side a may be tested. When the key S is not pressed, thelever 5 is against contact 4, so that V is connected as anordinary voltmeter. 31. A ground detector that is suitable for high-tensionalternating-current systems is shown in Fig. 39. This is mm T TH1 I rrrrr T xm i Fig. 39. one of the earlier types
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