Week 1 Flashcards
Other names for power station
Power plant
Generating Station
Generating plant
What is Power station
An industrial facility for the generation of electric power and generally connected to an electric grid
What is a generator ? And what creates current?
A rotating machine that converts mechanical power into three-phase electric power
Current :
Relative motion between a magnetic field and a conductor creates current
Give examples of source harnessed to turn the generator
Burning fossil fuels like:
coal , oil, natural gas
Clean energy:
nuclear power , renewable energy like: solar, wind, wave, geothermal, hydroelectric
Why are 3 phase AC generators the workhorse of the power generation plant?
They’re not power limited as DC generators
+
Voltage-level shifting is less expensive using AC transformers
Power transformer:
Definition
Used in :
Used to transfer electrical energy in any part of the circuit between the generator and distribution primary circuit.
Used in transmission and distribution to interface step up and step down voltages
Distribution transformer
Performs the last voltage transformation in a distribution grid.
Converts voltage used in transmission lines to one suitable for household and commercial use (down to 240 v)
Power transmission line
Definition :
Consists of:
Overhead , structure used in electric power transmission and distribution to transmit electrical energy across large distances.
Consists of one or more uninsulated electrical cables (multiple of 3 for 3phase) suspended by towers or poles
Powe distribution lines and underground cables
Stepped down voltage in BH standards:
Distribution network consists of:
Voltage at utility customers delivery points:
66kV / 33KV / 11kV
Distribution network can consist of overhead electrical lines and underground cable systems
Voltage at utility customers delivery points may require further reduction or stepping down, either by utility transformer or customer owned and operated transformers to 400 3ph and 230 1ph
Feeder In
Electric power distribution:
Electrical wiring circuit in a building:
In electric power distribution:
Voltage power line transferring power from a distribution substation to the distribution transformer.
In electrical wiring circuit in a building:
A wire/line that carries power from a transformer or switch gear to a distribution panel.
Quality and safety of an electrical installation will be assured only if:
(3)
1- the design is done according to the wiring rules
2- the electrical equipment comply with relevant product standards
3- initial checking of conformity of the electrical installation with the standard and regulation has been done
When is Initial testing of an insulation is done?
Before a utility will connect an installation to its supply network, strict pre-commissioning electrical tests and visual inspection by the authority or by its appointed agent must be satisfied
Pre-commissioning electrical tests and visual inspection checks for installation in buildings includes : (5)
1- electrical continuity and conductivity tests of protective, equipotential and earth bounding conductors
2- Insulation resistance tests between live conductors and the protective conductors connected to the earth arrangement
3- tests of SELV (safety extra low voltage) and PELV (protection by extra low voltage) circuits or for electrical separation
4- Insulation resistance/impedance of floors and walls
5- protection by automatic disconnection of the supply
Periodic check and testing of an insulation must be performed by:
And how? (4)
By authorized agents
1- verification of RCD ( residual current device) effectiveness and adjustments
2- appropriate measurements for providing safety of persons against effects of electric shock and protection against damage to property against fire and heat
3- confirmation that the installation is not damaged
4- Identification of installation defects
What is Bahraini electricity Regulation No. 303 ?
All electrical switchgear and accessories shall be so designed and manufactured to operate continuously in the electricity supply system of Bahrain having :
Nominal voltage: 400/230 volt +6% 3ph 4 wires
Frequency: 50 Hz + 2%
Neutral arrangement: solidly earthed
Installation earthing : TT system as per ICE 60364-3
Maximum prospective fault level: 50kA (31 MVA) at 400 v and short time duration of 0.5 s (maximum)
What are the characteristics of the electricity supply system at 11 kV?
Nominal voltage: 11kV +_ 6% 3ph 4 wire
Frequency: 50 Hz +_ 2%
Neutral arrangement: the system neutral is connected to earth through a low resistance at the sending end station
Maximum prospective fault level: 20 kA (350 MVA) at 11kV for a short time duration of 1 s maximum
Transmission voltage level
220kV , 500kV
Secondary transmission voltage level
66kV , 33kV , 11kV
Voltage level for residential and commercial use
400v/230v
Primary distribution voltage level
11kV , 13 kV
