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(i) Differential relays
The differential relay responds to vector difference between two or more similar
quantities.
- The differential relay has at least two actuating quantities say I1, I2
- The two or more actuating quantities should be similar i.e. current 1 & current 2.
- The relay responds to the vector difference between two i.e. I1~ I2 which includes
magnitude and/or phase angle difference.
Differential protection is generally a unit protection. The protected zone is exactly
determined by location of CTs. The vector difference is achieved by suitable
connection of CT or PT secondaries.
(ii) Inductive Interference in Transmission lines:
Inductive interference depends upon gradient of voltage at surface of conductor or
corona. The inductive reactance affected from conductor attenuation at 1000 kHz
varies from 0.3 to 0.9 dB/mtr.
(iii) Nickel cadmium cell
Nickel cadmium cells employ a solution of potassium hydroxide in distilled water as
electrolyte with a specific gravity of 1.200 at 16oC.
- Anode: NiOH and specially treated graphite
- Cathode: CdO, Fe2 O3
Cadmium oxide or iron oxide.
- AV. Voltage 1.2 V/Cell
1.3 V/Cell when fully charged.
The condition of battery can be determined with a voltmeter during charge or
discharge, while charging Ni-Cd battery, the temperature of electrolyte should not be
allowed to exceed 46oC. The battery does not bubble the gas until after the first
41/2 hrs when charging at the 7 Amp rate. No finishing rate is needed. The voltage of
charger should not be above 1.85 volt per cell.
gregorymasila answered the question on February 22, 2018 at 16:25
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