Relay,Cable

 Plug in type Relay-

These relays are plugged in to pre-wired terminal boards.It works on electromagnetic principle. Each relay has a base electromagnet,armature,contact spring contacts, transparent cover and handle.A non magnetic residual pin is fixed on the inner face of armature,in all  relay except magnetic latch relays.

When current is applied through the coil,it sets a magnetic flux through the bar magnet,core,L shape heelpiece and armature.

The flux causes armature to attract towards pole face.  Armature picks up and front contact closes.The residual pin maintains small air gap in attracted position.When current interupts, magnetic flux collapse. The contact spring above the armature helps restoring to its full released position thus front contacts open.

Plug in type Relay consist of more than 25 varieties. Out of which about 12 variables are used on Indian Railway. These relay normally operate on 12,24 and 60 volt DC and can be provided with max of 16 independent contacts.

Polycarbonate material is used for relay cover of Q Series relay.

Non Fusible Contacts- A pair of contacts in which one contact element comprises non fusible material which presents practically no risk of welding of contacts.eg metal to carbon relays. 

Carbon Contacts- Corbon in the expression  ' Corbon to metal contacts ’ is used as general term covering graphite and compounds and mixtures of carbon and metals.

Metal Contacts - Metal in the expression ' Corbon to metal contacts ' and 'Metal to Metal  contacts' is used as a general term covering the use of silver,silver cadmium oxide,tungsten, platinum or any other suitable material to an approved specification.

Track Relay - Track relay are relays which is directly connected across the rails of the track to detect occupation of track. E.g QT2,QTA2,QBAT.

Line Relay- Line relay are used for any other purposes other than track circuits such as HR, DR, NWKR. E.g QN1,QNA1

Dependent Contact-  The condition in which a movable arm contact connecting front contact when the relay is energized and the same arm contact connects to a back contact when the relay is denergized. 

Independent Contact- The condition in which the movable arm contact connects to either a front or back but not both.

Pickup Value(operate value)- The value of current or ampere turns which is just sufficient to close all the front contacts of relay under specified conditions.

Drop away Value ( Release Value)- The value of the current or ampere turns at which all the front contacts get open under specific conditions.

Wiping ( Self cleaning) contacts- Contacts designed to have certain relative motion,during the interval from instant of touching until completion of the crossing motion.

QNA1 ac immunity is 1000 V.

It's front contact will not make when AC rms voltage 1000V, 50 hz  applied across relay coil.

It's back contact will not break when AC rms voltage of 300 V,50 Hz is applied across the relay coil.current 115mA.

Coil Resistance is 200 ohms

QBA1  - DC baised AC immunised relay, used for NR and BLR of TLBI.A Copper slug is provided on the core for immunization and a permanent magnet is provided on the core for biasing.It does not operate if 20 times of the rated voltage is applied.It's specification is BR Spec No 932 A.used in Daido.

QTA2 - Pick up voltage  1.40 V and pick up current is 140 mA.

Minimum Excitation is 125% of rated pick up voltage.Maximum  Excitation is  300% of rated pick up voltage.

Copper slug is provided on core to achieve AC immunity.Due to this Copper Slug , it requires more DC power to pick up.Hence it requires more time to pick up and drop due to copper slug.

It can be used upto 450 m track circuit in REc area with choke at both ends.

Coil Resistance- 9 ohms.

AC immunity- 50 V AC.

QBAT -2F/2B

Pick up voltage 1.75 v,Pick up current should be 175 mA.

Minimum Excitation is 122% and Maximum  Excitation is 235% of rated pick up voltage

Coil Resistance- 9 ohms

AC immunity- 80 V AC.

It can be used upto 750m Track Circuit lengths with choke in RE Area.

QNN1 ( DC Twin Neutral Relay)

Both relay are independent from each other.

Coil Resistance 470 ohms.

QBCA 1 Relay - QBCA 1 relay contact can carry 30 amps. AC immunity of 1000v,50 Hz AC.Used to drive point motor. It is biased and AC immunised Relay used for heavy duty contact

 2F 4B (30 Amp/ 3 Amp)

Coil Resistance- 250/910 ohm (24/50 DC)

Full pick up/ release- 19.2/2v DC (40/4v DC)

Contact Resistance- 0.1/0.2 ohm   

It is similar to QBA1 Relay but two heavy duty contact.

For spark quenching, blow out magnets is provided.

Minimum front contact pressure is 56 grams instead of 28 grams.   Specification no 943 A.    

QSPA1 Relay -

BR specification 933A

Only this relay is permitted to be used as repeater for immunised Q series track relays,due to its slow to pick up character.

Provision of a Copper slug between the core and heel piece for AC immunity and a magnetic shunt between the core and the armature at the front contact make this relay slow to pickup by 540/600 seconds.less slow to release by 140/200 seconds and immune to AC

QN 1 Relay - Used for all control and detection circuit.  Except in external circuits of AC RE area.

Coil Resistance-400 ohms

Specification no BR 930A

AC immunity for 300v 50 hz AC.Current is 60mA

QS3 Relay - 

Works on low current, works on 12 v DC. 

Coil Resistance 1000 ohms, current 12mA.

BR specification 930A

QB3 Relay -

Similar to QS3 Relay

It is biased Neutral line Relay. Two relays of this type is used in in parallel on tokenless block to detect line current polarity in place of polar relay.

Biasing stands good for 240 v DC.

QB 3 - 60 v dc, used in push button block instrument.

Contact resistance of Q series relay - 0.20 ohms 

Relay arm contact - Silver oxide

Arm contacts are movable.

Metal to Metal Relay

K 50 Relay :- 

K 50 Relay are available only in group units of different sizes.They are broadly classified as

Mini Group, Minor Group and Major Group.

Mini Group - 2 Neutral control relays or 2 Interlocked relays or ECR with power conversion unit

Minor Group-

Upto 15 relays.

Major Group -

Used only in RRI

Upto 30 relays.

Group Relay in Siemens interlocking 

a) 2 Aspect Signal Group

b) 3 Aspect Signal Group 

c) Shunt Signal Group 

d) Universal Route Group 

e) Point Group for PI

f) Point Group for RRI

g) Point Chain Group for RRI.

Non AC immunised Neutral Relays

These relays are available in 4F/4B , 5F/3B & 6F/2B contact configuration.Ohmic values of these relays are 1260 ohms, 1260 ohms,1840 ohms for 6F/2B.

Interlocked Relays-

These relays are available in 4F/ 4B, 5F/ 3B & 6F/2B contact configuration. The ohmic values of these relays are 615 ohms.

ECR pick up current= 108 mA/ AC 50 Hz

ECR Drop away current= 72 mA/ AC 50 Hz

Cable-

Laying -

1) Main cable laid parallel to track shall normally be buried at a depth of 1.0 m from top of cable to ground level.The depth shall not be less than 0.50 m for tail cables.

2) When cables are to be laid in Rocky area,  depth of 1.0 m is not feasible.

3) Signalling cable must be separated from LT power cables by array of bricks or any other approved mean and from HT power cables a minimum 3 m seperation shall be maintained.

4) Where it is necessary to take the cables between tracks, it shall be carried in trunking/duct/pipe kept sufficiently below the ballast level.

5) Outside the station section, the cables should be generally be laid at not less than 5.5 meters from centre of nearest track.

6) Within Station section, the trenching to be done at a distance not less than 3 meters distance from centre of track.

Laying in RE Area

1) If the  depth of cable is not greater than 0.5 m, then the minimum distance of 1 m shall be maintained between cable and OHE structure.

2) When the cable is laid at a depth greater than 0.5 m,the minimum distance of 3 m shall be maintained between cable and OHE structure.

If we can not maintain above distances, the cable should be laid in DWC/HDPE pipe/ Concrete Ducts or any other approved means for a distance of 3 m on either side of the mast.If we follow this procedure the distance between cable and mast may be reduced to 0.5 m.

3) Near Traction Sub Station and feeding post- 

Minimum Distance between cable and any metallic part of OHE/ Earthing of sub station - 01 meter

4) Cable should be laid in Concrete or DWC- HDPE pipe/ RCC pipe for a length of 300 m on either side of feeding point.

5) The use of GI pipe or any form of metallic pipe is prohibited within a distance of 300 m from feeding post.

Spare Conductor-

Adequate spare conductors to a minimum 20% of the total conductors used in each main cable upto farthest point zone.

Beyond this there should be a minimum of 10% of spare conductors of the total conductors used.

No spare conductors are required if total conductors used is 3 or less.

Testing of Cables - 

All Conductors in Signalling cables must be tested for their insulation in dry weather once in three years provided cables are monitored through ELD else annually preferably before monsoon.

Tail cable should be tested for insulation once a year.

Periodical Testing

Main Cable - Every 2 years

Tail cables - Once in year

Spare Conductors - once in year

Cable markers distance - 20 m in station Section 

50  in block section 

20 percent Spare for farthest point.