Primary devices

Busbar The busbar is the centre of the substation. That is similar than a bus exchage, the meeting point, there meet everybody. The busbar is evetytime under voltage, if you want service the busbar hou have to switch off it, because of it on the most substations are two busbars. The busbar can be from aluminium or copper prifiles, from aluminium pipes or from aluminium cables. Some substations use coated pipe busbars, the indoor substations use aluminium profile ones, the old outdoor substations use aluminium cables on portals with stain susmension Insulators, the new outdoor substations use aluminium pipe busbars on post Insulators. There is an aluminium pipe busbar on 120 kV

Switching I: Switchgear The switchgear is a switching device which select the current's way. You can't switch current with the switchgear, you can only select the way then that circuit is current free. That is similar than the rail track switches on the railway, you can switch when the switch is train free, if you use it when the train is on it, the switch and the train will break. We could buld in breakers which can break currents but a switchgear's price is 1/10 part of a breaker. You have switchgears at home, you can disconnect anything with the sockets and plugs. The second function of the switchgear: the voltage decontaminating. When you want decontaninate a part from the voltage, you gave to disconnect the sevction with switchgears and ground it. A 120 kV switchgear If you open a switchgear under current, you will see that and you must buy a new switchgear: Grounder knife: The grounder knife or switchgear is a simple one witch either pole is on the ground. They are mostly on the side of the switchgears. You can close it, an arm goes up into the second connector when the normal switchgear is open.

Switching II: Breaker The breaker is the current breaker device or power switch. The breaker havve to able for break high fault currents, switch back onto fault and break the faults. A breaker have to be fast, it have to break the arc fast. That is similar than a cannon or a big gun: A motor wound on a spring or a punp makes high pressure in a container, when the breaker get switching command, the ON or OFF relays trips the hammer and the breaker "shots", it open or close the connectors inside. Something have to break the arces: mostly in the new breakers are SF6 gas (Sulphur-hexafluorid), on the old breakers are oil or vacum. You have breakers at home too, check you fuse board, there are small automatic breakers. There are two 220 kV, SF6, spring shoter breakers

Transformer The transformer is the soul and the most expensive of a substation, the voltage steeping point. I think everybody know it.. All big transformers are oil cooled ones, there are two types: pump oil circulated or natural circulated. There are different electric types of transformers: Mormal two coils ones on the small substations or Booster type one coil transformers on the big substations witch works than a huge potentiometer. All transformers on the substations have tertiary coils, mostly on 6, 18, 30 kV witch suplies the power supply of the substsation and the paralell coils. All big transforers have grade-switches, that is the regulation of the secondary voltage. A 400/120/18 kV, Booster type, 250 MVA transformer

Measuring transformers: In a substation are big voltage and current values, we can't measure them directly, we bave to build in devices witch make indirect harmonic values, they are 1 A and 200 V nominal values on the most substations. Two secondary device types use the secondary measuring circuits: the mesuring devices (all measurings) and the relay devices (protections). One measuring transformer has more secondary colis (cores). There are two types od measuring transformers: paper-oil or SF6 gas insulated. The small indoor measuring transformers are in epoxy coat. There are exist combinated measuring transformers, one device has current and voltage cores too. Current transformer: The current transformer makes 1 A from 1000 A or 2000 A or from somemany wat you want. Because of the big transformation and the big primary currents the primary coil is one rod, on round of that rod is the scondary coil. The primary current has to flow cross the measuring transformer. The secondary devices are in serial in the current measuring circuits. A current measuring circuit is grounded in one point because the circuit's voltage can lift up. The current measuring core is alike than a current generator, it keeps the actual current value. If the measuring circuit opens, the core lifts up the voltage and it can make hard sparks or the measuring transformer can blows up. If you want service a secondaty device, you have to put a short circuit onto the core. (That is similar than the big and small cog wheels, if you stop the hard big one, it breaks the driver small fast one) Voltage transformer: That is an easy tranformer, it's cores give only voltage for measuring and for relays. They are simple circuits with fuses. One secondary device has one fused voltage circuit. Two types of voltage measuring circuits exist: the either grounds the star point (neautral), and the second one grounds the L2 phase (L1 and L3 are on line voltage, the neutral is on phase voltage, the L2 is on ground). The voltage transformer measures the primary phase voltage from the ground. A 400 kV field sevtion: Forking devices

Paralell coils: The transmission lines are long, with the ground that is a huge capacitor. The capacitor generates lot of reactive power, we have to put somewhere it, the paralell coils drain it.

Arrestor: That is a primary protection device. It is a varistor mostly with a spark space. If the volage goes above a limit, it makes ground fault, conduct down the currents by the relative higher voltage, under the voltage limit it close Wave locker coil: That is a dam for the superpolated waves on the transmission line. The inside communication goes on the transmission lines by superpolated waves, they have to stay in their transmission line.

Indoor substation types: Open cells: The switchears, breaker, measuring transformers are in the cell, the busbars are the to pof them, the cable lines are bottom. Coated cells: The busbars and the busbar switchgears are inside top, the breaker is a car in the rack, you can pull it out, that is the disconnecting, the cable line and the measuring transformers are bottom.