Railway Signal Engineering

  Resetting  - 1. Block Section/ Auto/IB Section-   Preparatory Reset by both side ASMs.Will show clear only after matching 'count in ' and 'count out’ with passage of train. 2. Main Line/ Run through line-   Preparatory Reset by on duty ASM only. Will show clear only after matching 'count in ' and 'count out’ with passage of train 3. Point zone/ loop line/siding -  Conditional Reset by on duty ASM and another operating staff. Will show immediately clear after operation. As per RDSO Specification, life of Digital Axle Counter shall not be less than 20 yrs

IB Signal  - IBS is an arrangement made for increasing the section capacity by splitting of a relatively long block section into two portions namely Rear Section and Advance Section by placement of IBS at  near mid of two block sections. IB is used where distance between two block sections is equal or more than 10 kms.MSDAC is possible in IB Section. IB signal should not be placed if Gradient is steeper than 1:80.  In case of IB signal, Separate set of ATs shall be provided,with automatic Changeover switch . Rear Section i.e. " Station Controlled Intermediate Block Section" starts from LSS of rear station and ends at IBS including 400 m block overlap in that direction. Advance section i.e. " Block Controlled Intermediate Block Section" starts from IBS and ends at Home Signal of Advance Station including block overlap in that direction. Track sections in both Rear and Advance Section are monitored either by Axle counter or Track Circuit. Train entry into Rear Sec...

Earth is a Equipotential surface. All power equipments along with suitable SPDs are to be connected to Earthing having earth Resistence less than 1 ohms. LPZ ( Lightening Protection Zone) - Outer Zone LPZ 0- Zone where the threat is due to unattenuated lightening electromagnetic field. LPZ 0 is sub divided into  LPZ 0A- Zone where threat is due to direct lightening. LPZ 0B - This Zone is protected against direct lightening.  Internal system will be subjected to partial lightening surge current. Inner Zone -  Area inside structure  LPZ 1-  Zone inside structure where magnitude of surge current is reduced due to multiple parallel paths and isolating surfaces and or by installing SPDs. LPZ 2..n - Zone inside structure where magnitude of surge current may further reduced  by current distribution and isolating surfaces and or by installing SPDs. Surge Protection Device  - Class A -  This is provided with an external lightening conductor on top of ...

Earth Resistance  Earth Resistance of an earth is sum of three separate resistances a) The resistance of the conductor joining earth electrode to the installation. b) The contact resistance between the surface of the earth electrode and the soil  c) Resistance of the body of soil surrounding the earth electrodes. The first two resistances are negligible compare with third. So resistance of the earth is primarily depends upon nature of soil and not by electrode itself. d) Material used for a standard electrode system should be corrosion resistant.Under ordinary soil conditions, use of galvanized iron or mild steel electrode is recommended. If soil corrosion is likely to be excessive, it is preferable to use either copper or copper clad electrode. The electrode shall be free from paint,enamel or greese. e) Earth tester normally used for measurement of earth resistivity comprises of the current source and meters in a single instrument and directly read  the resistance v...

       All roads should be preferably cross the Railway line at Right angles. In special cases,when modification is required to suit the Road approaches, the angle of crossing should not be less than 45 degree.( pway manual =906). Minimum width of Road- Special class -7.5 m,others -5.5 m OHE Height of contact wire - 5.50 mts to 5.75 mts from Rail level.Under bridge it is 4.65 m. This height can be reduced to 4.54 m if carriage department certifies that no rolling stock above 4.27 m height will move on that line All interlocked level crossing gates should be kept 'Normally open to Road traffic’.( pway manual =907).  Periodical census once every three years. This shall be carried out for 7 days by Engg,traffic and SnT. Train/ Four Wheeler/ Bullock Cart/Tonga - 01 unit. Cycle Rikshaw/Auto Rikshaw - 0.50 unit Spl class gates- TVU more than 50000 A Class gates- TVU 30000-50000   or Line Capacity utilization is 80% ( on Single line section) and no of Road ve...

  As per new SEM,  Minimum length of Track Circuit is 26 m( Two rail length) Glued joint Insulation  Resistance- Not more than 25M ohms in dry conditions and not less than 3 k ohms in wet conditions. Glued joint are to be replaced after 250 GMT ( Gross million Tonnes) of Movement of Traffic. Stray Voltage - not more than 10 m Volt  track circuit upto 100m. 100mV for track circuit more than 100 metres. Stray current -  Not more than 10 mA for TC upto 100 Mts.  Not more than 100mA for length of TC is equal or above 100 mts. B type choke for 25 KV AC RE Area- 120 ohm impedence and 3 ohm Resistence. QTA2 - pick up voltage 1.40 v ,  pick up current should be 140 mA.Minimum Excitation is not less than 125% of rated pick up voltage.Maximum  Excitation is not less than 300% of rated pick up voltage for plug in type Track Relay. Configuration 2F1B.AC immunity is 50V AC. QBAT - pick up voltage 1.75V, max pick up current should be 175 mA.Minimum Excitatio...

  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...