T2 Flashcards
In relation to intruder alarm system, describe the operation of the two following intruder alarm detection devices:
- panic button
- interia sensor
PANIC BUTTON: a panic button is compromised of a set of closed contacts latch by a key. When the panic button is pressed by a person a duress signal is generated by the alarm, regardless if the system is set or unset. When the system is reset after the alarm, the panic button is restored with a key and the alarm contacts close again.
INERTIA SENSOR: an inertia sensor consists of a gold plated ball seated in a pair of contacts which close the alarm circuit. An impact to the frame of door which the inertia sensor is mounted on will move the ball and open the circuit thus raising the alarm.
Name three types of fire alarm warning devices and give one suitable application for each?
Bell - school
Horn - factory
Siren - noisy factory
In relation to the design and installation of fire alarm systems:
A) state what the fire alarm system categories L, P & M define
B) list suitable locations within a building for the installation of the main control panel
C) state the maximum floor area for a single fire detection zone
D) state the maximum alarm sound level in DB
A) L, automatic fire detection systems intended for the protection of life.
M - a manual system that does not use automatic detectors
P - automatic fire detection systems intended for the protection of property
B) at entry/exits of buildings, at fire service access points and at the control panels at either of the two locations listed above.
C) the zone shall not exceed a floor area of 2000 meter squared
D) 118 db
List the benefits of electrical smart metering for both consumers and electrical utilities operators?
- Captures real time electrical energy consumption.
- facilitates more accurate profiling and future energy predictions energy customer.
a) what are the three main advantages of using instrument transformers?
1) enables the uses of standardised instrument
2) increase safety, as the secondary side of the transformers can be connected to earth
3) with the use of suitable short-circuit switch, and the use of voltage links, measuring instruments can be exchanged without the need to isolate the electrical supply
state 4 advantages of MCBs in comparison with fuses?
1-do not normally require replacement.
2-do not age service.
3-tamperproof.
4- single phasing of motors is eliminated.
give any five advantages of using all insulated switchgear versus metalclad switchgear
1- reduce shock risk
2- reduce size
3- good corrosion resistance
4- non tracking
5- not necessary to provide earth continuity between boxes
a- state two advantages and disadvantages of copper busbars when compared to aluminum busbars.
a- Advantage
- higher conductivity than aluminum busbars
- higher mechanical strength in tension
disadvantage
- much heavier than aluminium busbars
- more expensive than aluminium busbars
b) when selecting supports for a busbar system describe three characteristics that need to be considered.
- they must be capable of withstanding the electromechanical forces resulting from the rated short circuit current of the switchboard
- they must not compromise the insulation resistance between the busbars and between the busbars and earth
- they must accommodate expansion of the busbar without incurring mechanical stress
a- identify the three main effects of lightning strike.
- electrical effects
- side flashing mechanical effect
- thermal effect
b- when assessing a building for a lighting protection system, list five factors that must be considered.
- use of the structure
- contents of the building
- the location of the structure
- the nature of the surroundings
- type of construction
state two main functions of UPS systems. (b) when selecting a rotary, diesel powered UPS system for an office block, list two factors that need to be considered before installation of the system.
a) - to provide a backup supply in the event of mains failure.
- to provide a conditioned electrical power supply free from spikes surges, harmonics and other disturbances
b) - noise
- fuel storage
in relation to potentially explosive atmospheres state 3 ways in which combustible dusts can be ignited by electrical apparatus
- by mechanical sparking of friction or heating associated with the apparatus
- by radiated energy
- by electrical discharge of an accumulated electrostatic charge
in relation to the installation of electrical circuits in potentially explosive atmosphere’s define the term intrinsically safe circuit
a circuit may be defined as intrinsically safe both the current and voltage are limited to such an extent that no spark or thermal effect can cause a potentially explosive atmosphere to ignite. the zener diode becomes conductive at a defined voltage level. this limits the voltage Vl in the potentially explosive area. a resistor connected in series limits the maximum supply current Il to the load in the potentially explosive area.
when verifying the operation of a grid tied micro generator at the commissioning stage, list the tests that are required to be carried out in the accordance with En50438, ESB NC6.
- the operation of the micro generator under/over voltage protection device.
- the operation of the micro generator under/over frequency protection device.
- loss of mains detection, the shutdown of the micro generator until the public network is restored.
- operating range, to ensure the micro generator is operating fully within range
