SU1238988A1 - Device for protecting direct current contact system wires - Google Patents

Description

The invention relates to the relay protection of wires of a contact network of urban electric transport against overloads and short-circuit currents causing overheating of the contact wires above the permissible temperature and their failure due to annealing.

The aim of the invention is to improve the reliability of the protection of the wires of a contact network of direct current.

The drawing shows a block diagram of the device.

The device for protection of a contact network contains a current sensor 1 connected through a threshold element 2 to a key element 3, the output of which is connected to the protective-disconnect element 4, an additional threshold element 5, a control signal driver 6, made on an RS trigger, a delay element 7 made on an RC circuit, a voltage divider 8, the midpoint of which is connected to the input of element 4, made with a time delay.

The device works as follows.

The signal from current sensor 1 is fed to divider 8 and, depending on the output level of trigger 6, fed to element 3, passes to disconnecting element 4 either halved or unchanged. If the input of the element 3 from the trigger 6 receives the signal “O, it is closed and the signal from the sensor 1 passes through the divider 8 to the element 4 reduced twice. In this case, disconnecting element 4 simulates the heating of the contact wire during normal operation, which is characterized on average by the uniform distribution of the load current between the wires of the contact network.

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If the signal "1" arrives at the input of the element 3 from the trigger 6, then it is open and the signal from the sensor 1 passes through the element 3 to the disconnecting element 4 without changing. In this case, the heating of the contact wire in the event of a short circuit in the contact network is simulated under the assumption that the entire current of the contact network passes through one contact wire.

Trigger 6 is controlled by the signals of elements 2 and 5. If element 5 detects an increment of current in the contact network that exceeds the setpoint (which is typical of a short circuit in the contact network), then the trigger 6 from element 5 receives a signal that sets its output to “1. If the current in the line is less than the setpoint (which should be taken below the minimum short circuit current), which indicates the absence of a short circuit in the line, then the output of element 2 generates a signal that sets the output of trigger 6 to the “O” state.

In switch 4, a signal is generated that is proportional to the heating temperature of the contact wire. If it exceeds a certain level, element 4 is triggered, the output of which is the current protection output.

A device for protection of catenary wires differs from such protections in consideration of the uneven distribution of short-circuit current in wires of a catenary network, which ensures high protection of the device and makes it possible to increase the lengths of sections to achieve acceptable voltage drops, eliminate annealing of contact wires and increase reliability power supply traction loads.

Claims (1)

DEVICE FOR PROTECTING DC CONTACT NETWORK WIRES, comprising a current sensor, the output of which through a threshold element is connected to the input of the key element, the output of which is connected to the input of the protective shutdown element, characterized in that, in order to increase reliability, it is equipped with an additional threshold element, a shaper a control signal made on the RS-trigger, a delay element made on the RC-circuit, a voltage divider, the middle point of which is connected to the input of the trip element made with delay time, and its extreme points - to the output of the current sensor, while the output of the RS-trigger is connected to the input of the key element, its direct input is connected to the output of the additional threshold element, and the reverse - to the output of the first threshold element, and the input of the additional threshold element is connected to the midpoint of the delay element, _{l the} extreme points of which are connected to the output of the current sensor. SU „„ 1238988