Capstone AT3 Flashcards
Provide two methods for verifying the result for maximum fault loop impedance
Measure external and internal circuit, Zs and refer to table 8.1
Measure the internal circuit, Rphe and reference to table 8.2
Explain the term ‘equipotential bonding’ and the reason it is essential, and provide an example where it would be expected to be installed if doing a visual examination on a domestic residence?
Equipotential bonding is intended to minimise the risks associated with the occurrence of voltage differences between exposed conductive parts of electrical equipment and extraneous conductive parts
An example includes the distribution system load current in the soil passing through a swimming pool
AS/NZS3000 clause 5.6.2.6.5 and clause 1.4.60
What is a service distributors requirement for interrupting capacity (KA rating) of protective devices in an installation
Protective devices installed by the customer shall have an interrupting capacity adequate for the prospective short circuit current at the point of installation
A likely cause of electrical shocks from the metallic water system in premises with a MEN earthing system is
A: an open circuit in the neutral conductor supplying the water heater
B: a short circuit to earth of a final sub-circuit active conductor
C: a high resistance in consumers supply neutral conductor
D: a short circuit in a sub-circuit protected by a re-wireable fuse
C: a high resistance in consumers supply neutral conductor
What would be the consequences of the absence of an MEN link under normal conditions and fault conditions
The circuit under no fault conditions would operate as normal with no electrical shocks
Under fault conditions there would be a high electric shock hazard
Describe the parts
1 = PEN
2 = Mains In
3 = FSB active
4 = FSB neutral
5 =FSB earth
6 = MEN
7 = main earth conductor
When does an installation require an earth stake to be installed
When an active and neutral is supplied, but a protective earth is not.
Fill in the correct words for the following statements
1 - functional
2 - bonding
3 - protective
The purpose of . . . Earths is to allow enough current flow under fault conditions to trip the circuit breaker
The purpose of . . . Earths is to reference earth to enable a device to operate
The purpose of . . . Earths is to reduce potential differences between accessible parts
The purpose of protective earths is to allow enough current flow under fault conditions to trip the circuit breaker
The purpose of protective earths is to reference earth to enable a device to operate
The purpose of bonding earths is to reduce potential differences between accessible parts
There are alternate earthing systems that may be required to be used by local supply authorities, these differ from the MEN earthing system in common use in Australia, what is the MEN earthing system used in australia
A: TN-C-S
B: TT
C: TN-C
D: TN-S
E: IT
A: TN-C-S
When a separate overload protective device and a short circuit protective device are used for the protective of a circuit, such as for the consumers mains at a domestic residence, what are the requirements for co-ordination? In addition please provide the relevant AS/NZS 3000 clause
The energy let through by the short circuit device does not exceed what the overload device can handle
AS/NZS 2.5.6.2
Using AS/NZS 3000
A: state a cause of overvoltage in an electrical installation
B: suggest a method of protective against overvoltage
A: an insulation fault between the electrical installation and a circuit of higher voltage, i.e switching operation, lightning
B: the use of a surge protection device
Using the AS/NZS 3000
A: state a cause of undervoltage in an electrical installation
B: suggest a method of protection against under voltage
A: overload, conductors of inadequate cross-section, fault in HV supply
B: under voltage relays or releases operating a switch or a circuit breaker or contactors
In a domestic residence, all final sub-circuits must be RCD protected, the RCDs will operate to disconnect supply when the earth leakage value reaches
A: 20mA
B: 30mA
C: 100mA
D: 10mA
B: 30mA
When will an RCD not operate under fault conditions
An active neutral fault that does not involve an earth path
Clause 2.3.6.2 from the AS/NZS 3000 relates to the which of the following functions
A: devices for shutting down for mechanical maintenance
B: mechanical maintenance of electrical equipment
C: manual isolation
Devices for maintenance of maintainable equipment
A: devices for shutting down for mechanical maintenance
What is the danger associated with removing an open circuit metering transformer and what safety measures should be taken
A: high voltage across the transformer terminals
B: short circuit the terminals before removing
Give one requirement for an emergency switching device. In addition please provide the relevant AS/NZS 3000 clause
A single switching device directly interrupting the incoming supply;
or a combination of several items of electrical equipment operated by one single action resulting in the removal of the hazard by interrupting the appropriate supply
