Electrical safety for high rise building.

1. ELECTRICAL SAFETY FOR
HIGH RISE BUILDING
PREPARED BY :
B. S. SHAH

2. Safety rules to be followed in a Multistoried building.
Following are the basic fire safety measures required in any multi-storey building as per
the National Building Code(NBC):
 Fixed carbon-di-oxide/foam/dco/water spray extinguishing system must be placed
and maintained in easily accessible places in buildings.
 Proper Fire alarm system must be installed at each floor in all buildings of 15m. and
above in height, and residential buildings above 24m. Height.
 Electrical codes shall be complied with to prevent overheating, ignition due to
electrical faults, short-circuits.
 Every building shall have a fire exit at every floor which will be directly connected to
ground. It should be an external staircase separate from the main entrance. It should
be built with fire proof or non-combustible material.
 A down comer is a pipe for fire fighting made within a building which is directly
connected with the water tank on the terrace of the building.
 Installation of dry riser to provide water at each floor in the event of fire.
 Proper storage of hazardous and flammable materials which are needed in the
building to avoid fire.

3.  Conduct fire drills at regular intervals to understand the evacuation process in case of
fire. These drills shall be done in the presence of a qualified fire officer and trained
staff.
 Periodic inspection of buildings by authorized officer for violations, making sure that
orders are complied with, prosecution or closure of buildings that are not complying.
Safety precaution in electrical installation of multistoried buildings
A multistoried building is defined to be a building, which is more than 15 meters in
height. A number of very serious incidents of fire have occurred in these multistoried
buildings. Many of these fire were initiated by faults or involved the electrical system. As
such utmost precautions are necessary to be taken in sub-stations and distribution
system etc. for multistoried buildings
(1) Sub-station :
• Sub station with oil capacity more than 2000 litres shall not be located in the
basement where oil cannot be drained. If it is required a sub-station in the basement
in the separate fire resistance room of 4 hours fire rating. The room shall be at
periphery of the basement. The enterence to the room shall be through a fire
resistance door of 2 hour fire rating. A crub or still at suitable height shall be provided
to prevent the flow of oil from the transformer room to other parts of the basement.
There shall be an access to the transformer direct from out side. The switch gear shall
be sepsrate from the transformer by installing it in a separate room, the separating
wall being of not less then 4 hours fire rating. The transformer shall be protected by
automatic hihg velocity water spraying syetem.

4. • when the transformer is located at ground-floor level it shall be separated from the
building by a wall of 4 hours fire rating.
• Oil filled transformer shall non be located on any floor above the ground floor.
• Where the oil capacity exceeds 2000 litres a soakpit consisting of an RCC tank capable of
accomodating entire oil shall be provided
(2) Distribution system:
• There shall be at least two rising mains. Each shall have a change over switch for
connections of to either of the mains.
• Independent feeders shall be provided for critical installations like fire pump etc.
• The cable duct shall be closed at every alternate floor with combustible material having
the same fire resistance as the duct.
• Water mains, telephone mains, intercom lines, gas pipes or other service lines shall not
be laid in the duct for the electric cables
• Separate circuits from the main switchgears panelsshall be provided for water pumps,
lifts, staircase and corridor etc.these circuits shall be laid in separate conduits so that fire
in one circuit will not affects the other.
• The staircase and corridor lighting shall also be connected to alternate sources.

5. Stand-by generating set:
Stand-by generating set should be provided to supply the emergency load in case of failure
of mains. Emergency load will consist of emergency lighting, fire pump and fire fighting
equipment's and other critical loads.
Fire safety:
Fire fighting arrangements as required by reverent regulations are to be provided. A
manually operated electrical fire alarm system shall be installed with one or more call boxes
located at each floor. The call boxes shall also be so located that they are easily accessible
and no occupant is required to travel more than 22.5 meters to reach a call box
Conduct safety tests as per IE.
High Voltage Test (Dielectric Voltage-withstand Test)
This test is carried out by applying a significantly higher than operating voltage to the device
under test. In this test, the insulation of a product, stressed to a greater extent than under
normal operating conditions, should not be breached for the product to pass. In most cases,
the device is stressed to twice its normal operating voltage. During type testing, i.e. testing
during designing a product or for a double insulated product, however, much larger voltage
may be applied. For all electrical products, the high voltage test is a universal test, meaning
that every unit should pass before it can be used.

6. Insulation Resistance Test
This test is to measure the total resistance of a product’s insulation by applying a voltage of
500 V – 1000 V for low voltage systems. The minimum acceptable value of resistance for a
product to pass an insulation resistance test is 1 mega ohm (1000 kΩ. The insulation
resistance test is not a substitute for the high voltage test. Many standards and safety
agencies have specified this is a universal test for all products. This test may also be carried
out after every maintenance procedure or repair.
Earth Continuity Test
This test is performed by measuring the resistance between the third pin (ground) and
outside metal body of the product under test. The maximum acceptable value is generally
0.5 ohms although certain standards may specify 0.1 ohms. This test is generally carried out
at a slightly higher current (e.g. 25–60 A) so that the ground bond circuit maintains safe
voltages on the chassis of the product, even at a high current, before the circuit
breaker trips. This test is essential so that the product does not cause an electric
shock resulting from insulation failure. In India current specified is 16 A so the test is done
at double of the current i.e. 32 A.
Leakage Current Test (Line Leakage Test)
This test is to measure the undesirable leakage current that flows through or across the
surface of the insulation or the dielectric of a capacitor. This test is generally carried out at
100%-110% of the rated input voltage of the product under test. The maximum acceptable
limit of a leakage current is generally 210 micro amperes. At first, this test was mandatory
for medical devices only. On Fluke 6500-2 there tow options for this test. 200mA and 25A

7. FIRE ALARM SYSTEM
• How do addressable and conventional
alarms differ?
Every device connected to the addressable system has its own
unique address. When a fire is detected, the device’s address
shows up on the main control panel, telling you exactly which device
has been activated. This will enable you to find the exact location of
a fire and extinguish them quickly.
• With a conventional system, there is no way of pinpointing the exact
location of the fire. However, by wiring your building into different
zones, you can get a general idea of where the fire is. For instance,
if you have two floors, you could wire the first as ‘zone 1’ and the
second as zone 2. So if a fire occurs in zone 1, you know that the
fire is somewhere on the first floor.

8. Wiring differences
• Addressable alarm systems connect devices using a loop. This is
where one wire connects all devices to the control panel. Both ends
of the wire loop connect to the control panel.
• With a conventional alarm, each device will be connected to the
control panel via its own wire, rather than a shared one. One end of
the wire will be touching the device, and another touching the control
panel.

9. Which is more reliable?
• The addressable alarm panel is also the more reliable of the two.
This is because the wire connects to the control panel at both ends
(see the diagram above). If one end of the loop becomes severed,
signals can still be sent to the control panel via the other end of the
loop. Loop isolation modules are also used to separate devices on
the loop. This means that if one device becomes disconnected, it
won’t disable the circuit. With a conventional system, if a wire has
become severed, the device will become disconnected.

10. SMOKE DETECTOR