rail circuits

                   Classification and types of track circuits


Electric rail circuits (RC) are used to continuously check the condition of rail track sections on tracks and stations (vacant or busy sections, rail integrity). Some types of RCs are also used to transmit code signals of automatic blocking (AB) and signals of automatic locomotive signaling (ALSN).
The main elements of the RC are: DC or AC power supply; limiting (active or reactive) resistance; choke transformers (in areas with electric); rails with butt and rail connectors; insulating joints to isolate individual parts of rail threads; track receiver (track relay).
Rail circuits are divided according to the main features: purpose – distillation (AB or PUB), station, for humps, for automatic fencing devices; switching circuits – normally closed and normally open (for sorting slides);
the type of signal current – direct and alternating current (frequency 25, 50, 75 Hz and tonal frequency);
power supply – with continuous, pulsed or code;
type of rail line – unbranched and branched;
use of rails for the passage of traction current – two- and single-strand;
type of traction – for electric, direct current, alternating current and autonomous traction;
track receiver type – for direct current with a neutral, polarized or combined relay; for AC with single or dual element (phase sensitive) relay;
the method of superimposing ALCH code signals — with continuous superposition (code AB) or with a preliminary one (at stations when specifying a route);
the place where the ALCH code signals are applied is from the supply, relay ends, or both ends of the RC.  There are three main modes of operation of the RC: normal, shunt and control. In normal and 
the shunt modes are controlled respectively by the free and busy rail lines of the operational RC by wheelsets of the rolling stock; in the control one is fixed a break in the rail of the RC.
The following types of RC are used at stations and hauls (recommended for use are marked *; length of track chains in meters are shown in brackets; lengths of unbranched RCs in the numerator are in the numerator, branched equal to the sum of the lengths of all its rail sections):

AC current frequency 50 Hz:
a) station:
impulse with traveling relays IRV-110, IMVSH-110 — in the areas of removal from the code AB and ALSN with a frequency of 25 Hz with electric alternating current and at the junction stations of two kinds of electric traction (1200/900);
phase sensitive with a track relay DSSH-13 – in areas with EC, code AB and ALSN of 25 Hz frequency with AC electric current, at the junction stations of two kinds of electric thrust (1200/500) and with autonomous thrust (1500/900);
phase-sensitive with pre-coding at a frequency of 50 Hz with a track relay DSSH-13A – in areas with code AB and ALSN with a frequency of 50 Hz with an electrical alternating current (1200/750);
phase-sensitive with the imposition of ALSN with a frequency of 50 Hz with a track relay DSSH-13A – in areas with a code AB and ALSN with a frequency of 50 Hz with an autonomous thrust (1200/700);
b) distillation:
coded with the traveling relays IRV-110, IMVSH-110, IVG – on the hauls, areas of removal (approximation) of stations with AB and ALSN of 25 Hz frequency with electric alternating current (2500).  

AC current frequency of 75 Hz:
a) station:
impulse with traveling relays IRV-110, IMVSH-110 — in the sections with EC, DC and ALSN of 75 Hz frequency with electric alternating current and at the junction stations of two kinds of electric traction (1250/900);
b) distillation:
code track with IMVSH-110 track relay – in areas with code AB and ALSN of 75 Hz frequency with AC electric current (2500).

AC current frequency 50 Hz:
a) station:
single-track with traveling relays НВШ1-800 (НМВШ2-1000/1000), ANVSh2-2400 – on non-coded paths in the necks, short sections of receiving-sending tracks with direct current electric current (900/500);
single-phase phase-sensitive with a track relay DSSH-12 – on non-coded paths and necks with direct current electric current  1100/500);
two-phase phase-sensitive with the traveling relay DSR-12, DSSH-12 – in areas with code AB and ALSN with a frequency of 50 Hz with an electric dc charge (1500/700) and an autonomous thrust (1500/900);
stationary with track relays НВШ 1-800, НМВШ2- 900/000 (НМВШ2-1000 / 1000) – on the main receiving-departure ways and switch-line sections of lines with EC, AB and ALSN with frequency of 50 Hz at autonomous thrust (1500/750) ; with small-sized equipment and with traveling relays ANVSh2-2400 (НВШ 1-200), НМВШ2- 900/900 (НМВШ2-1000 / 1000) – on receiving-departure ways and switch sections with АБ and АЛСН with frequency of 50 Hz with autonomous thrust (1500 / 500);
phase-sensitive with a capacitor in the local element circuit “1 with track relays DSSH-12, DSSH-13 – at intermediate stations in the presence of backup power from the battery and semiconductor converters with autonomous thrust (1500/900);
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