Line Test Device
LTD line tester (hereinafter referred to as LTD) is designed to detect short circuits in 3.3 kV DC supply line (feeder) of electrified railways traction networks.
LTD is designed according to classic circuitry used in railways. LTD includes a supply transformer that supplies high voltage rectifier circuit and provides galvanic isolation between the contact network and 220 V AC power supply network.
LTD monitors the state of contact network by the residual resistance between contact wire and rail. If this resistance is high (for example, when auxiliary equipment or rolling stock heating facilities are on), the current flowing from LTD does not reach the trip threshold, and this allows switching of the feeder automatic device and its automatic reclosing.
LTD has two NC/NO contacts for connection to the control circuit of high-speed circuit breaker. LTD trip threshold is set by a variable resistor through a hole in the device housing. A LED located next to the resistor is provided for easy setting.
The power supply circuit does not require an additional stabilizer: accuracy of line resistance measurement does not depend on the level of 220 V AC supply voltage.
Technical parameters
LTD technical parametersDocuments
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