Genset

Guide

1 2
 54,000 die-hard fans
Liverpool FC
Bespoke power solutions
since 2015

John Kinstrie
Head of Power Solutions

3 4
Company Introduction

DTGen is the UK’s leading generator specialist. We supply, We are recognised industry expert in a variety
install and maintain diesel and gas generators across the of sectors including:
country, providing our customers with products and support • Health
throughout the lifecycle of their generator set. We are backed • Retail stores and distribution centres
by a global generator manufacturer with a wealth of experience • Data centres
in the power industry. • Rail
• Utilities
Whatever your power requirement, you can trust us to meet it. • Construction

Operating from our 6.3 acre head office facility, our 80,000 sq ft
Our solutions department offers comprehensive turnkey
warehouse space accommodates workshops, parts distribution solutions from initial concept design through to on site
depot, a dedicated training station, the biggest load test cell commissioning and client training in:
in the country and the largest stock of generators in the UK. • High/low voltage power generation
• Multiple set and multiple mains synchronising systems
We hold up to £2m of generators in stock, from six to 3,000kVA • Sound attenuation and ventilation systems
– this ensures that we can quickly react to provide the right • Bespoke acoustic enclosures
solution for your power needs. • Bulk fuel storage tanks and transfer systems
• Extended exhaust systems
• Power management systems
Our team of experts, including high voltage and skilled • Associated civil works
service engineers, operate the length and breadth of the • Electrical and mechanical installations
country providing comprehensive support across a range
of industry sectors.

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 Generator Basics

40,000 students & staff

City of Glasgow College
Silent rooftop backup generator since 2012
7 8
Generator Basics Rating Definitions
Ratings are typically defined in terms of
The KW rating will never change but the kVA
rating is variable depending on the power
maximum power available, average load factor, i.e.:
factors, hours of usage per year, peak demand
and typical applications. These broad 800 KW machine at 0.8 PF 1000 kVA
definitions are intended to cover a wide range
Generator Set 800 KW machine at 0.9 PF 888 kVA
of industrial and commercial uses.
Diesel generators typically consist of five main components: 800 KW machine at unity PF 800 kVA

The two main ratings applicable to most

projects are: Load Acceptance
Unlike the utility supply (the grid) a standby
Prime generator is not an infinite supply and
1 These ratings are applicable for supplying therefore load needs to be steadily applied to
5
continuous electrical power (at variable load) prevent an engine from shutting down.
2 in lieu of commercially purchased power.
There is no limitation to the annual hours of Smaller naturally aspirated machines typically
operation and these models can supply 10% below 100 kVA have greater load acceptance
overload power for 1 hour in 12 hours. capability in the region of 70 to 100%.

Standby Larger turbo-charged machines up to 2.5 mVA

These ratings are applicable for supplying have less capability on first step acceptance in
continuous electrical power (at variable the region of 50 to 65%. Alternative engines are
load) in the event of a utility power failure. available to accept loads of up to 80%, however
No overload is permitted on these ratings. these engines are either oversized or far less
The alternators on these models are peak competitive than main source readily available
3 continuous rated (as defined in ISO 8528-3). machines.
4
Manufacturer’s product ratings can differ, the Generator manufacturers specify their engine
most commonly used in the UK for standby performances to ISO 8528-5 class G2.
application is prime power otherwise known
as PRP. A 1000 kVA PRP rated machine could With the introduction of load control and
1. Control Panel 4. Baseframe therefore also be rated as follows. UPS systems, stepping the load onto a standby
Electronic controls / Steel base frame with generator at circa 50% of its output power
instrumentation panel anti-vibration mounts should not create any operational issues.
PRP: 1000 kVA 800 KW
and output breaker
Standby: 1100 kVA 880 KW
5. Radiator
2. Engine Mechanically driven All manufacturers rate their machines as kVA
1500 RPM, 50 Hz cooling package to output based on a power factor of 0.8 lagging.
Industrial diesel engine keep the set at optimum To convert kVA to KW multiply by 0.8
temperature (kVA x 0.8 = KW).
3. Alternator
Brushless, 50 Hz,
3 phase alternator
9 10
Noise levels A diesel generator with an operational water Noise Levels
heater and fully charged batteries should An open generator set will produce a noise
receive a start command and run up to speed / level at 1m of approximately 100-120 dBA.
voltage within 10 to 15 seconds at which stage This noise is emitted from various sources as
the first step load can be applied. Once the illustarated below:
engine has stabilised circa three to five seconds
later the remainder of the load can be applied, For most installations this is not viable and
i.e.: fully loaded generator within 20 seconds attenuation is then required. The industry
from a mains failure signal. standard reduction is to 85 dBA at 1m in

ise
assumed free field conditions. This level is
ise

No
No

It is recommended that that a diesel generator

e
suitable for most installations however

in
n
Fa

g
En
is loaded to at least 60 % of its prime rating special considerations must be taken into
to avoid any issues relating to light loading, account when the installation is in an area
which is typically carbon build-up on the where planning applications are required.
cylinders caused by un-burnt fuel on light load Typically residential areas fall into this category
applications. and the noise level must then be reduced
further. Noise levels can be reduced to 60 dBA
High Velocity High Velocity Operational Requirements at 1m in assumed free field conditions.
Air Flow Air Flow Generator sets require two key elements to For larger engines, 65 dBA is a more realistic
function correctly: target noise level.

1. Clean supply of fuel. If the fuel is not of good

quality, the risk to the engine is filters being
blocked and the engine not running, reduction
in engine performance and reduction in engine
life expectancy.

2. Ample amounts of cool air for combustion

and engine/alternator cooling. If the
alternator and engine are starved of air, the
engine will overheat and shutdown. Possibly
causing damage to the engine/alternator. The
air supply should come from the rear of the set
and be drawn over the complete unit.

11 12
Methods for reducing noise: When reducing noise, important considerations General Maintenance Should the site load be less than 30–40%,
must be taken into account. Each method, It is recommended that the end user of a it is recommended that an artificial load bank
• Attenuation (sound absorption)
excluding distance, has its own associated standby generator system starts the generator be brought in on an annual basis to run the
• Vibration isolation restriction to airflow and we must ensure that on a weekly basis and allows the machine to generator at 100 % load – this will prevent
• Barriers this restriction does not exceed that which run for five to ten minutes offload to prove that carbon build up.
the cooling system is capable of overcoming. the machine is operational and is likely to start
• Distance
We must also take into consideration that in the event of a mains failure signal. The load bank can either be connected at the
we do not generate flow noise. This can be LV switchgear by disconnecting the output
generated when we are trying to force ventilate Once a month, a mains failure simulation test cables from the generator circuit breaker or by
an enclosure or plant room and typically is should be carried out and the generator run on fitting a secondary load bank breaker.
generated when the louvers or attenuation are the available site load for up to one hour. This
sized incorrectly. will prove that the changeover arrangement is The additional set mounted three pole load
operational and that the generator can support bank circuit breaker would be fitted with a
For comparison 85 dBA is equivalent to medium the site load. shunt facility to automatically disconnect the
traffic and 65 dBA is equivalent to a modern load bank in the event of a mains failure during
day dishwasher or office conversation. On a quarterly basis, the generator supplier / a load test. This will allow the generator to
specialist should be called in to carry out the supply the building load and not the artificial
manufacturers recommended maintenance load bank.
checks including any oil and filter changes that
may be necessary.

-13 dBA -13 dBA -17 dBA -20 dBA -23 dBA -26 dBA -28 dBA -29 dBA -31 dBA -32 dBA -33 dBA -34 dBA

1m 5m 7m 10m 15m 20m 25m 30m 35m 40m 45m 50m

Noise reduction – Distance

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Installation Methods The most cost effective solution is to install a Air Flows
Generator sets can be installed using various standby generator external to the building at Generators require high volumes of air for cooling purposes and combustion.
different methods. Various considerations ground level within a standard build, acoustic The position of the air inlet and outlet louvres should ideally be on opposite
should be taken into account when deciding enclosure or container. external walls to create cross-flow ventilation across the entire generator set.
which type of installation method is to
be chosen. Some key considerations are The position of the generator should be The radiator has an engine driven cooling fan which pulls air into the room/
as follows: such that a hi-ab vehicle or crane can easily enclosure via the inlet louvre and then pushes the air out of the room/enclosure
offload. The machine should be positioned via the outlet louvre, which is connected to the radiator via a flexible plenum to
1. Cooling requirements to create cross approximately 1.5 metres clear of any other prevent re-circulation into the plant room/enclosure.
flow ventilation buildings / obstacles for maintenance access
2. Access for installation and maintenance and airflows. The louvre sizes will depend on the cooling airflow, duct allowance and noise
3. Noise levels level and would typically measure between 700mm W x 700mm H for a small 50
Types of installation in order of preference kVA to a 3.5m W x 3.5m H louvre for a 2.5 mVA.
Installation methods: to cost, lead time, practicality and future
• External canopied generator set maintenance:
(Standard canopy)
• External drop over enclosed generator set 1. Externally located within a canopy
or container Air flow
(for special noise applications)
• External containerised generator set 2. Ground level plant room with two
• Plant room installation external walls
3. Roof top external canopy or container
4. Roof top plant room set with two
external walls
5. Internal or basement plant room
with restricted outside walls

Typical examples of cooling airflow requirements:

30 kVA: 65 m³/min 80 kVA: 125 m³/min 100 kVA: 190 m³/min
150 kVA: 230 m³/min 200 kVA: 310 m³/min 250 kVA: 350 m³/min
350 kVA: 400 m³/min 450 kVA: 480 m³/min 500 kVA: 500 m³/min
700 kVA: 1150 m³/min 1000 kVA: 1200 m³/min 1250 kVA: 1250 m³/min
1500 kVA: 1300 m³/min 1700 kVA: 1950 m³/min 1800 kVA: 2100 m³/min
2000 kVA: 2100 m³/min 2250 kVA: 2300 m³/min 2500 kVA: 2900 m³/min

Note: Typical duct allowance (back pressure) would be in the region of 25mm water gauge/250 pascals
15 16
Fuel & Fuel Storage Systems Most readily available fuels will have a Generator sets up to 800 kVA typically come The engine’s fuel system works on a continuous
Diesel generators run on red diesel, which small bio content of up to 5 %, this does with base mounted fuel tanks with capacities ring which requires a feed line from the base/
is readily available via all fuel distribution not affect the operation of the engine or the ranging from 8 to 12 hours based on 100% free standing tank and a return line to the base/
companies. The specification of this fuel should manufacturer’s warranty. Guidance should load running. free standing tank. This is to allow any unused
be based on diesel fuel with a specific gravity of be taken for higher bio contents which may fuel during combustion to be returned to the
0.84 and conforming to BS2869, Class A2. require additional filtration or an alternative Due to torsional vibration at start up, tank as shown below:
engine type. generator sets above 800 kVA require free
Winter grade fuel oil is recommended for the standing fuel tanks.
UK as it has a lower waxing temperature (circa Diesel generators are not very efficient with
-15°C) than standard diesel. only one third of fuel burnt being converted
into electrical power. The remaining is lost via
heat from the cooling package and the exhaust
system as shown below:

Heat loss Common Rail Fuel System

–4 st
30 hau
0%
Ex

Radiator
Electricity 33%
20–40%

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Bulk Tanks & Transfer Systems Where the bulk fuel tank is feeding a base/day Fuel Consumptions
Where the standard base tank providing 8 to tank via gravity, fuel transfer controls are then Fuel consumption figures at 100% rated load (for guidance only)
12 hours of fuel storage is not enough, bulk required. Float switches would be installed
fuel storage tanks are then required. A typical into the generator base/day tank and these 10 kVA 4 Lts 300 kVA 60 Lts 1000 kVA 220 Lts
example of this is on NHS sites where their would be installed at preset levels. The float
30 kVA 7 Lts 350 kVA 70 Lts 1250 kVA 260 Lts
HTM specification requires 200 hours of fuel switch would call fuel on and off when the
internal floats reached certain levels within 60 kVA 14 Lts 400 kVA 80 Lts 1350 kVA 280 Lts
storage on site.
the base/day tank. At the feed from the bulk 80 kVA 19 Lts 450 kVA 95 Lts 1500 kVA 300 Lts
To achieve applications like these we introduce tank a motorised ball valve would be installed. 100 kVA 22 Lts 500 kVA 100 Lts 1700 kVA 350 Lts
bulk fuel storage tanks, these range in size This valve will control the flow of fuel. The fuel 135 kVA 30 Lts 550 kVA 110 Lts 1800 kVA 380 Lts
from 500 litres up to 100,000 litres plus. Various system control panel would signal the valve 150 kVA 40 Lts 600 kVA 120 Lts 2000 kVA 425 Lts
types of bulk fuel installations can be utilised, open or close depending on the level of the
200 kVA 45 Lts 730 kVA 150 Lts 2250 kVA 470 Lts
the most common methods are as follows: float switches in the base/day tank.
250 kVA 55 Lts 800 kVA 165 Lts 2500 kVA 530 Lts
• Bulk fuel tank directly feeding generator set
• Bulk fuel tank feeding base/day tank via Where the bulk fuel tank is feeding a base/
For generators running at lighter loads, consumption figures can be adjusted on a pro-rata basis,
automatic gravity feed (bulk tank must be day tank via a pumpset, further fuel transfer e.g. 500 kVA: 100 Lts / Hr @ 100% load = 75 Lts / Hr at 75% load and 50 Lts at 50% load.
at a higher level) controls are required. Float switches would
• Bulk fuel tank feeding base/day tank be installed into the generator base/day tank
via automatic pump set (single pumpset and these would be installed at preset levels.
or duplex) The float switch would call fuel on and off
when the internal floats reached certain levels
Where the bulk tank directly feeds the within the base/day tank. At the feed from the
generator sets engine, no enhanced controls bulk tank a motorised ball valve and pumpset
are required. A feed and return fuel line is (single or duplex) would be installed. As the
float switches call the fuel on and off via the Bulk Tank Transfer System
required as previously detailed under fuel and
fuel storage systems. fuel system control panel, the pumpset will
run and the ball valve will open. When the fuel
command is off, the pump sets will not run and
the ball valve will be closed.

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Exhausts Exhaust flue diameters will vary in size from There is no legislation stating the final position
The exhaust fumes must be discharged to 50mm dia to 700mm dia depending on the or height of a standby generator flue, but
atmosphere and where practical take the engine size, noise level, route length and good engineering practice should always be
shortest route to avoid any unnecessary bends number of bends. applied and particular care should be taken
in the system - excessive bends and long to avoid personnel contact and fumes venting
distances create back pressure restrictions on An engine will either have one or two exhaust into windows/air intakes. The ideal location of
the engine. This can be overcome by increasing manifolds depending on the type and size, but an exhaust termination point is above the air
the bore/diameter of the flue. typically generator sets up to 800 kVA have discharge louvre as the high volume air passing
single manifolds and above 800 kVA to 2.5 mVA through the louvre will assist in diluting the
Exhaust gases can reach temperatures of up to have twin manifolds. fumes or alternatively extend the flue to the
600°C; therefore care must be taken to avoid highest point of the building.
heat transfer onto any building structures/ Exhaust gas flow rates will range from
surfaces and also to ensure that the gas is not 5m³/minute for the smallest generator set to
discharging onto any personnel access areas. 600m³/minute for a 2.5 mVA generator set.

When mild steel flues are installed, they should

be lagged with mineral wool insulation and
over clad. An alternative to mild steel flues and
commonly used in the industry is the pre-
fabricated twin wall insulated stainless steel
flue pipe systems.

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 External
Generator Sets

4 million passengers per day

Network Rail
Power generator supplier since 2006
23 24
 External Generator Sets Specification and features of an standard canopy:
• Manufactured from galvanised steel
• Removable end panels allow access to
radiator, exhaust outlet and alternator rear
• Advanced powder coating paint finish • Doors positioned for optimum access to
• Single piece main roof frequently serviced items
• Baseframe extends beyond enclosure • Secure, lockable doors prevent
protecting against handling damage unauthorised access to control panel,
Standard Canopy Sets • Minimal external fixings exposed to fuel fill and battery
Most generator manufacturers have a standard range of acoustic environment • Emergency stop button mounted on
enclosures, these typically reduce noise to levels of 77 to 85 dBA • Zinc plated fasteners exterior, convenient to control panel
at 1m and are usually available for generator sets ranging from • Corner posts and air handling units • Cooling fan and battery charging alternator
30 kVA to 800 kVA. These provide the most cost effective solution manufactured from high grade composite fully guarded
for generator installations. material
• Side hinged doors on both sides of the Bespoke Canopy Sets
enclosure incorporating lift-off hinges at Where the standard canopy set cannot be used
45 degrees due to special noise constraints or generator
• Radiator fill via removable, flush mounted sets greater than 800 kVA, bespoke built drop
rain cap fitted with compression seal over canopies can be used. These are designed
Canopy set • Lube oil drain valves / coolant drain valves based on the specified noise level and site
constraints. Please note these enclosures will
be larger than the typical dimensions.
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Bespoke drop over canopy set

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Typical dimensions:

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33 kVA – 65 kVA: 2.3m L x 1.2m W x 1.6m H (1,300 Kg)

e
88 kVA – 110 kVA: 2.8m L x 1.2m W x 1.6m H (1,600 Kg)
150 kVA – 220 kVA: 3.6m L x 1.2m W x 1.9m H (2,300 Kg)
250 kVA – 330 kVA: 4.3m L x 1.4m W x 2.2m H (3,600 Kg)
400 kVA – 700 kVA: 5.4m L x 2.1m W x 2.3mm H (5,800 Kg)
730 kVA – 800 kVA: 5.9m L x 2.4m W x 2.7mm H (9,500 Kg)
25 26
Realistic maximum reductions in noise: Containerised Sets Bespoke built containers can also
33 kVA – 65 kVA: 60 dBA at 1m in free field conditions For external generator sets typically be made to suit sets smaller than
88 kVA – 110 kVA: 60 dBA at 1m in free field conditions
above 730 kVA, containerised 730 kVA with reductions in noise
150 kVA – 220 kVA: 60 dBA at 1m in free field conditions
generator sets are used. These are possible to a level of 60 dBA.
250 kVA – 330 kVA: 60 dBA at 1m in free field conditions
400 kVA – 700 kVA: 65 dBA at 1m in free field conditions bespoke built depending on the The industry standard noise level
730 kVA – 800 kVA: 65 dBA at 1m in free field conditions required noise level on site, which is 85 dBA and this noise level
800 kVA – 2,500 kVA: 65 dBA at 1m in free field conditions typically ranges from 65 dBA to also provides the most cost
85 dBA. Reducing the noise below effective solution.
65 dBA is not viable for sets above
730 kVA as the bunded container
floor amplifies the generator noise.

Typical specification and features of • Zinc plated fasteners

bespoke canopy: • Radiator fill via removable, flush mounted
• Manufactured from galvanised steel rain cap fitted with compression seal
• Walls and roof lined with mineral wool • Lube oil drain valves / coolant drain valves
retained by galvanised perforated steel sheet • Doors positioned for optimum access to
• Finish painted to BS4800/BS381C/RAL frequently serviced items
colour in two pack acrylic • Secure, lockable doors prevent
• End mounted extract attenuator with fixed unauthorised access to control panel,
blade weather louvres and bird mesh grill fuel fill and battery
• End mounted inlet attenuator complete • Emergency stop button mounted on
with fixed blade weather louvres and bird exterior, convenient to control panel
mesh grill
• Six personnel access doors complete with Please note bespoke drop over enclosures
panic release bolts do not have a floor and are designed to be
• Both ends removable installed directly onto a flat concrete plinth.
• Roof mounted or box type gas exhaust
silencer assembly
• Cable entry gland plate
• Minimal external fixings exposed to
environment

27 28
Typical specification and features of • Multi-cable entry access points
containerised set: • Space for fully mounted floor standing
• ISO type container with corrugated side breaker (>900 kVA)
sheets fully welded construction • Internal luminous panic release buttons
• Corner castings fitted to all eight corners on doors
• Fully bunded floor adhering to UK Defra. • Emergency stop button located
Container floor with capacity for all engine conveniently by each personnel access door
oil, coolant and on board fuel • Floor with textured non slip heavy duty
• Walls and roof lined with 75mm thick surface for safety and durability
mineral wool retained by galvanised • Day fuel tanks up to 3,000 litre
perforated steel sheet • Shot blasted and finish painted to
• Two personnel access doors complete BS4800/BS381C/RAL colour in two pack
with panic release bolts are included for acrylic painted to our standard paint
access to the generator specification 004
• Inlet end removable • All external components and surfaces
• Fully integrated AC lighting and power treated with anti-corrosion coatings
distribution system
• Inboard or roof mounted gas exhaust
silencer assembly

Typical dimensions (85/80 dBA standard container):

33 kVA – 250 kVA: 6.1m L x 2.5m W x 3m H
275 kVA – 700 kVA: 6.1m L x 2.5m W x 3m H
730 kVA – 1700 kVA: 9.2m L x 2.5m W x 3.2m H
1750 kVA – 2500 kVA: 12.2m L x 2.5m W x 3.2m H

Typical dimensions (75/70 dBA standard container):

33 kVA – 250 kVA: 6.1m L x 2.5m W x 3m H
275 kVA – 700 kVA: 9.2m L x 2.5m W x 3.2m H
730 kVA – 1700 kVA: 12.2m L x 2.5m W x 3.2m H
1750 kVA – 2500 kVA: 14.2m L x 3.2m W x 3.5m H

Typical dimensions (65 dBA standard container):

33 kVA – 250 kVA: 9.2m L x 2.5m W x 3.2m H
275 kVA – 700 kVA: 12.2m L x 2.5m W x 3.2m H
730 kVA – 1700 kVA: 14.2m L x 3.2m W x 3.5m H
1750 kVA – 2500 kVA: 16.5m L x 3.2m W x 4m H

29 30
£200 million investment in the future
HSBC Headquarters

Plant Room
Silent basement backup generator since 2019

Installations

31 32
Plant Room Installations Ideal Room Layouts
The two examples below show the correct installation method. Air would be
drawn over the entire set and ensure correct alternator and engine cooling.

Acoustic Ventilation Equipment Where the equipment cannot be installed

When a generator set is being installed through the door way, the inlet or outlet louvre
internally, we require cross flow ventilation to can be oversized to allow plant installation and
achieve cool air for engine/alternator cooling removal.
and cool air for engine combustion.
Best practice is to install the generator set at
By creating air inlet and outlet apertures within ground level in a plant room with two external,
the wall, this results in noise break out via such opposite facing walls for cross flow ventilation.
holes and therefore plant room attenuation Special consideration must be taken by the
equipment is required. Plant room attenuation builder when constructing the plant room to
dampens the noise created by the generator ensure that it is constructed from acoustically
set and the air flow through the room. The compatible materials to prevent noise
size of attenuation is determined by the noise breakout through the walls and roof.
requirement and air flow required to keep the
generator set cool. The plant room should ideally have direct
vehicle access to it. This would allow the
Access to the room is normally through an delivery and offload vehicle direct access Incorrect Room Layouts
acoustic single/double door which can be for an easier installation. This also enables The two examples below show an incorrect installation method. Air would short
used for equipment installation/removal. In easier future maintenance, repairs and plant circuit the alternator and most of the engine causing heat spots. This in turn
some cases the door can be fitted with the replacement. would cause the generator set to shut down due to over heating.
attenuation built in.
X

33 34
Key Components of Careful consideration must be taken when 33 kVA to 220 kVA Plant Room Installations
designing a system incorporating all of the
Plant Room Installation
above items.
1. Generator set
2. Air inlet attenuator and fixed blade
weather louver
3. Air outlet attenuator and fixed blade Key considerations are:
weather louver • Ensure system is designed to
4. Exhaust gas silencer
account for all allowable
5. Exhaust gas silencer support stand/
steel work pressure drops and limits
6. Exhaust bellows • Ensure system provides
7. Exhaust flue tail pipe
adequate air for combustion
8. Flexible air outlet plenum/duct
and cooling
• Ensure adequate space for
mainetance access

Equipment dimensions:
Key components
Generator set: 2.6m L x 1.1m W x 1.7m H
85 dBA air inlet attenuator: 1.2m L x 1.2m W x 1.6m H
85 dBA air outlet attenuator: 1.2m L x 1.2m W x 1.6m H
Air outlet flexible duct: 0.4m L x 1.2m W x 1.6m H
Air inlet and outlet louver openings: 1.2m W x 1.6m H

Exhaust gas silencer: 1.5m L x 0.8m W x 0.8m H

Maintenance access around set: 1m
Recommended room dimensions: 6.4m L x 3.1m W x 3m H
Reduce noise from 85 dBA to 75 dBA: Increase Room Length by 0.6m
Reduce noise from 85 dBA to 65 dBA: Increase Room Length by 2.4m

Please Note: The above information is provided for reference only and can be treated as preliminary only.
It assumes that the plant room is at ground level with two external walls and is constructed of acoustically
compatible materials. Please contact sales@dtgen.co.uk for bespoke solutions or further information.
35 36
250 kVA to 330 kVA Plant Room Installations 730 kVA to 1000 kVA Plant Room Installations
Equipment Dimensions: Equipment dimensions:
Generator set: 3.3m L x 1.1m W x 1.9m H Generator set: 5m L x 2.1m W x 2.3m H
85 dBA air inlet attenuator: 1.2m L x 1.8m W x 2.2m H 85 dBA air inlet attenuator: 1.5m L x 2.4m W x 2.4m H
85 dBA air outlet attenuator: 1.2m L x 1.8m W x 2.2m H 85 dBA air outlet attenuator: 1.5m L x 2.4m W x 2.4m H
Air outlet flexible duct: 0.4m L x 1.8m W x 2.2m H Air outlet flexible duct: 0.4m L x 2.4m W x 2.4m H
Air inlet and outlet louver openings: 1.8m W x 2.2m H Air inlet and outlet louver openings: 2.4m W x 2.4m H
Exhaust gas silencer: 1.5m L x 1.2m W x 1m H Exhaust gas silencer: 2.5m L x 2m W x 1.5m H
Maintenance access around set: 1m Maintenance access around set: 1m
Recommended room dimensions: 7.1m L x 3.8m W x 3.7m H Recommended room dimensions: 9.4m L x 4.4m W x 4.4m H
Reduce noise from 85 dBA to 75 dBA: Increase room length by 0.6m Reduce noise from 85 dBA to 75 dBA: Increase room length by 1.2m
Reduce noise from 85 dBA to 65 dBA: Increase room length by 2.4m Reduce noise from 85 dBA to 65 dBA Increase room length by 3m

400 kVA to 700 kVA Plant Room Installations 1250 kVA to 1700 kVA Plant Room Installations
Equipment dimensions: Equipment dimensions:
Generator set: 3.9m L x 1.5m W x 2.3m H Generator set: 5.2m L x 2.2m W x 2.5m H
85 dBA air inlet attenuator: 1.5m L x 1.5m W x 2.2m H 85 dBA air inlet attenuator: 1.8m L x 3m W x 3.4m H
85 dBA air outlet attenuator: 1.5m L x 1.5m W x 2.2m H 85 dBA air outlet attenuator: 1.8m L x 3m W x 3.4m H
Air outlet flexible duct: 0.4m L x 1.5m W x 2.2m H Air outlet flexible duct: 0.4m L x 3m W x 3.4m H
Air inlet and outlet louver openings: 1.5m W x 2.2m H Air inlet and outlet louver openings: 3m W x 3.4m H
Exhaust gas silencer: 2m L x 1.5m W x 1.5m H Exhaust gas silencer: 3m L x 2.4m W x 1.5m H
Maintenance access around set: 1m Maintenance access around set: 1m
Recommended room dimensions: 8.3m L x 3.5m W x 4.3m H Recommended room dimensions: 10.2m L x 5.2m W x 5.9m H
Reduce noise from 85 dBA to 75 dBA: Increase room length by 0.6m Reduce noise from 85 dBA to 75 dBA: Increase room length by 1.2m
Reduce noise from 85 dBA to 65 dBA: Increase room length by 2.4m Reduce noise from 85 dBA to 65 dBA: Increase room length by 3m

Please Note: The above information is provided for reference only and can be treated as preliminary only. Please Note: The above information is provided for reference only and can be treated as preliminary only.
It assumes that the plant room is at ground level with two external walls and is constructed of acoustically It assumes that the plant room is at ground level with two external walls and is constructed of acoustically
compatible materials. Please contact sales@dtgen.co.uk for bespoke solutions or further information. compatible materials. Please contact sales@dtgen.co.uk for bespoke solutions or further information.
37 38
1750 kVA to 2500 kVA Plant Room Installations Mid Building or Roof Top Plant Rooms Basement Room Plans
Ground level installations are the most Similarly to mid building and roof top plant
Equipment dimensions:
economical and provide the best access for rooms, basement installations can also be
Generator set: 6m L x 2.3m W x 3.5m H initial installation and future maintenance. problematic.
85 dBA air inlet attenuator: 2.1m L x 3m W x 3.8m H However it is not always possible or practical to
85 dBA air outlet attenuator: 2.1m L x 3m W x 3.8m H install the generator set at ground level. Careful Key considerations when designing this type
Air outlet flexible duct: 0.4m L x 3m W x 3.8m H consideration should be given at design stage. of plant room, include:
Air inlet and outlet louver openings: 3m W x 3.8m H • Installation method – can the generator
The following key considerations must be and equipment be easily installed into
Exhaust gas silencer: 3m L x 2.4m W x 2m H
taken into account: the area
Maintenance access around set: 1m
• Size of crane required to lift the generator • Can the generator be installed as a single
Recommended room dimensions: 11.6m L x 5.3m W x 6.8m H into the plant room unit or is dismantling and re-building in situ
Reduce noise from 85 dBA to 75 dBA: Increase room length by 1.2m • The position of the crane at street level required?
Reduce noise from 85 dBA to 65 dBA: Increase room length by 3.2m • Are road closures required, how will they • Ventilation requirements – are there any
impact on programme/costs external walls?
• The overall weight and load of the • Duct work requirements – for air inlet and
generator being installed – plant room floor air discharge
must be supported • Plant replacement strategy in the event of
• Re-fuelling – fuel transfer system would be major plant failure
required introducing new costs to project • General access for regular maintenance
• Extended cable runs from the switchroom, • Re-fuelling – fuel transfer system would be
usually at ground level required introducing new costs to project
• Plant replacement strategy in the event of • Extended exhaust route required
major plant failure
• General access for regular maintenance As with roof top plant rooms, basement plant
rooms should only be considered when there is
Where possible ground floor plant room no possibility of installing the generator set in
installation should be used over mid building a plant room at ground floor level.
or roof top installation.

Please Note: The above information is provided for reference only and can be treated as preliminary only.
It assumes that the plant room is at ground level with two external walls and is constructed of acoustically
compatible materials. Please contact sales@dtgen.co.uk for bespoke solutions or further information.
39 40
Keeping you connected
Complex backup power

Control Systems
solutions for over 50 years

41 42
Control Systems Typical HMI/Scada Screen

Control Systems
Depending on the application there are various types
of controls and control philosophy that we would adopt.

The most common applications are as follows:

• Base load (no power on site, generator is only
source of power)
• AMF (automatic mains failure)
• AMF with no break return
• Full power control system

The above applications can be satisfied by the use of various

types of controllers. For the AMF and base load applications,
basic AMF, control panels can be used.

The range of digital control panels, combines straight forward

menu navigation with advanced metering and protection
technology. They are used in conjunction with transfer panels.

This allows you to monitor and control your generator set with
ease, whilst ensuring your unit operates within safe parameters
and provides important diagnostic information when needed.

When synchronising with the mains supply and power

management control systems, we can utilise various types
of control panels. The key three being ComAp, DSE and
Woodward EasyGen.

43 44
Base Load Application
Base Load Schematic
A base load application is when the generator set is the only
source of electric power on site. Typical examples where the
generator set is required to provide the base load on site are
as follows:
• Remote sites
• Offshore
• New construction projects where mains power supply has
not yet been installed
• Sites where the mains supply is not large enough for the load

Please see opposite schematic of typical base load installation.

Key notes:
• Basic key start generator control panel required
• Control panel to be manually operated at generator set
or operated via remote switch
• Generator breaker normally closed and distribution
panel supply breaker normally open (to prevent run up
against load)
• When generator is switched on, runs up to speed and
voltage, power available within approximately 15 seconds
• Once the generator is up to speed/voltage close the
distribution panel feeder breaker
• For periods where generator set will be off for pre-longed
periods of time (longer than 12 hours) a timer control circuit
will be installed – this will automatically start the generator
set allowing the starter battery to be charged
• When power is no longer required, the generator can be
manually switched off or the remote start signal removed

45 46
Automatic Mains Failure (AMF) Application
Automatic Mains Failure Schematic
Automatic mains failure application is when the generator
set is the secondary supply on site for use during a mains/utility
supply failure. This type of application is the most commonly
used in the industry and requires an automatic change over
panel in addition to the generator control panel.

Please see opposite schematic of typical AMF installation.

Key notes:
• The automatic change over panel monitors utility
supply voltage
• In the event of a mains utility failure, the changeover
panel sends a two wire start command to the generator set.
This start command is provided via the mains sensing unit
• When the generator receives this volt free start signal,
it automatically starts
• The generator runs up to speed and voltage and is available
to take load within approximately 15 seconds
• The changeover panel now sensing generator voltage,
opens the mains breaker and closes the generator breaker
to load the generator and supply the building load
• On return of a mains utility supply, the changeover panel
via the mains sensing unit starts a variable timer to ensure the
mains utility supply is healthy and not an intermittent return
• After the timer, and if the mains is healthy and present,
the changeover panel opens the generator breaker and
closes the mains breaker
• The mains utility supply now feeds the building’s load
• The generator runs on cool down and then shuts down
(approximately five minutes)
• Note at no stage are the supplies running in parallel,
interlocks are present between the mains and generator
breakers
• The changeover panel can either be a separate panel
as shown opposite or integrated in the distribution panel/
switchboard

47 48
Automatic Mains Failure (AMF) • On loss of utility mains power, the
generator control panel will monitor the Automatic Mains Failure With No Break Return Schematic
With No Break Return Application
loss of mains for an approximate period of
Automatic mains failure with no break return is
three seconds. If it is a true loss of mains,
when the generator set is the secondary supply
and not a brown out, the generator set will
on site. When the mains utility supply fails, the
then automatically start and provide a
generator set automatically starts and provides
signal to the DC power pack to open the
power to the building’s load as described in
mains breaker
the previous AMF application section. The
• When the generator set is up to speed
difference being, on return of the mains supply,
and voltage (approximately 15 seconds)
the generator set synchronises with the mains
the generator control panel will send a
utility supply and both the utility supply and
signal for the generator breaker to close
generator supply run in parallel for a short
and the generator set will then support the
period of time. The generator then ramps off
building load
and the generator breaker automatically opens
• On return of mains utility power, the
allowing the mains utility supply to take the full
generator control will monitor the mains
building load.
voltage for an approximate period of three
minutes
Please see opposite schematic of typical AMF
• After the timed period, and if the mains is
with no break return installation.
truly healthy, the generator control panel
will then begin to match the voltage and
Key notes:
frequency of the generator set with the
• For this application a more advanced
mains supply, this is achieved by speeding
generator control panel is required such as
up and slowing down the generator engine
– ComAp, DSE or EasyGen
via the electronic governor
• The generator control panel will control
• When the mains utility and generator
the full change over process however key
voltages then match, the generator control
items must be included by the switchboard
panel will send the signal to close the
supplier
mains breaker – the set and mains are now
• Key inclusions on switchboard – motorised
running in parallel
breakers (gen and mains), CTs and VTs for
• Within five minutes, the generator set will
mains and current sensing, DC power pack
ramp down and send the signal to open the
for breaker control, parallel limit timer and
generator breaker, the mains is now fully
G59 protection if not part of generator
taking the load and the generator set will
control panel
begin its cool down period
• The generator control panel monitors the
• The DNO (supply authority) will require
mains utility voltage and current through the
protections to be installed to ensure that
CTs and VTs installed in the switchboard
in the event of a fault either the mains or
generator breakers can be tripped open
(see below comments on G59 and parallel
limit timer)

49 50
G59 Protection Parallel Limit Timer
Example of full power control system:
When running in parallel with the mains utility A parallel limit timer is another type of
supply, the DNO (supply authority) requires protection device which should be used for this
additional protections to be installed. It is the type of installation.
responsibility of the client and not the DNO
to ensure these protections are installed. The The DNO dictates that for short term paralleling
DNO will witness test these protections on site time limits are in place for disconnection of
before permitting the generator set to run in one of the supplies. The parallel limit timer will
parallel with the mains supply. monitor the time the set and mains have run
in parallel and should this be longer than the
The DNO requires G59 protection to be installed programmed allowance, the parallel limit timer
at the point of set to mains synchronising, this will instantaneously trip the generator breaker.
is usually at the switchboard.
Full Power Control System
A G59 compliant mains protection relay is an Full power control systems can include:
electronic monitoring device which looks at • Multiple sets synchronising with each other
the quality and stability of the mains electricity. • Multiple sets synchronising with each other
It is programmed to certain fixed parameters and the mains utility supply
dictated by the DNO. These typically include • Multiple sets synchronising together and
voltage, frequency, ROCOF (rate of change of synchronising with multiple mains
frequency), phase angle and so on. Should • Single set synchronising with multiple mains
any of these areas go outside the programmed • Control of bus tie and feeder breaker
limits, then the relay will cause a protective • Full control of each type of system through
device such as an MCCB or other type of a dedicated HMI panel
circuit breaker to open, thereby instantly
disconnecting the generator from the grid. The preferred control solution for these types
of system would be utilising either the ComAp
The DNO will require a full G59 application to or DSE control modules.
be submitted prior to any installations or tests
taking place. The client should be aware that
there are costs associated with the application
and testing of this protective device.

51 52
 Jargon Buster

A matter of life and death

Complex backup power solutions for more
than 30 UK hospitals since 1988
53 54
 Combined heat and power (CHP) Delta
Air circuit breaker Backup protection
Use of a generating set or sets for the purpose of utilising the Usually associated with a winding connection configuration
Circuit breaker contacts open to the air (atmosphere); Type of protection intended to operate only after the main
heat produced (via the exhaust and the radiator) as well as of a transformer or electrical rotating machine where
see also circuit breaker. protective device(s) has failed to operate.
producing electricity. the three phase-coils are connected in series in a ê(delta)
configuration. There are a number of connection options
AC generator Base load
Compound generator for both three and four wire circuits e.g. open delta,
Electrical generator that produces alternating current The portion of load of a generator or building which
A generator whose excitation system takes elements of Edison delta, (sometime referred to as high-leg delta or
(preferred term). Aka alternator. is constant.
both voltage and current or derivatives of these in order to red-leg delta), and jack-leg delta etc. A two coil three wire
provide the required level of excitation to the main field. connection would be an open delta.
Active power Biodiesel
AC power with a unity power factor. Measured in watts. Diesel fuel with all or part content derived from
Contactor Deviation factor
vegetable oils.
An electrically operated heavy current switching device. The maximum instantaneous deviation of a generator
Alternator
voltage waveform, as a percentage of the true sine wave
Electrical generator that produces alternating current Black start
Cross current compensation of the same RMS value.
(non-preferred term). Refers to starting of a power system without the use of
System whereby the current loading of a generator in
an external power source, i.e. The building or application.
parallel with another is used to adjust the excitation of the Diesel bug
Amortisseur winding
second generator, so that the two generators share the load The generic term for the microbial growth found within fuel
Windings embedded in the pole face of a synchronous Brown out
equally, with minimum impact on the combined voltage systems and fuel storage tanks. Formed of a variety
generator, whose function is to dampen oscillations of the An intentional or unintentional drop in voltage in the utility
level. of different strains of fungi and bacteria.
pole due to cyclic irregularity and effect of load changes. mains power supply. Intentional brownouts are used
for load reduction in an emergency. The reduction may
Current transformer Diesel rotary UPS
Ampere last for minutes or hours, as opposed to short-term voltage
A current transformer will provide a reduced current, A diesel engine driven generating set which includes an
The unit of electrical current (amp). sag (or dip) lasting seconds caused by other factors. It is
(usually one or five amps) in its isolated secondary circuit electric motor driven heavy flywheel and AC generator.
known that such voltage drops can be harmful to certain
proportional to the current in the main circuit being In normal operation the motor drives the flywheel/AC
Analogue controls sensitive electrical devices, such as computers; therefore
measured. generator. When the mains supply fails the diesel engine is
Controls using variable voltage or current to pass accentuating the importance of a resilient backup regime
started and takes over from the motor, to drive the flywheel/
information. including a generating set for a business.
Cycle AC generator. The heavy flywheel keeps the system stable
The complete reversal of an alternating current or voltage whilst the engine is starting up.
Apparent power Bulk tank
from zero to positive maximum down to negative maximum
The product of current and voltage in an alternating current A large storage tank from which the generating set may
and back to zero. Dielectric strength
circuit which has a reactive element. take its immediate supply of fuel or may be used to provide
The maximum electric strength that an insulating material
a supply to a day tank.
can withstand intrinsically without breaking down. i.e.
Armature
Damper winding without experiencing failure of its insulating properties.
The assembly of windings and iron core in which the Bunding
More commonly used term for amortisseur winding.
generator output is produced. Sometimes referred to as This relates to the provision for containing leakage of fuel,
Differential protection relay
the Stator to avoid confusion. contaminated water, oil etc.
Day tank Relay operated by the current differential between two
A small storage tank from which the generating set takes points of a series connecting electrical circuit.
Asynchronous Busbar
its immediate supply of fuel. Often allowing for eight
Term applied to motors or generators which operate at Copper or aluminium (usually rigid) conductors of a
working hours and designed into the base frame of the Direct current
a speed not fixed by poleage and the supply frequency. rectangular, square, round or hollow section, to inter-
generating set. Current flow in one direction only i.e. no reversal polarity
connect high current circuits in a switchboard or building.
Attenuators
Decibels Droop
Devices for reduction of the emission of sound
Decibels dB or dB(A) are abbreviations for decibel. It is the Term used to describe the negative off-set of a reference
(also known as silencers). Circuit
“unit” for both sound pressure and sound power level. It is (usually that of frequency or voltage) with increasing load.
An electrical circuit is an interconnection of electrical
not a unit because it is the logarithm of a quotient. That’s In the context of generating sets the term is usually applied
Automatic transfer switch elements such as resistors, inductors, capacitors,
why Lp (pressure) and Lw (power) are both expressed in dB, to the governor or automatic voltage regulator and to the
A device used to automatically switch a power supply transmission lines and switches, with a power source and
each with a different reference and therefore unit-less. speed or voltage reference respectively. Introducing a droop
from normal to emergency when a power failure occurs a closed loop return path for the current.
The A is a weighting value, as in dB(A), but this is not characteristic for frequency and voltage is one method that
supported by ISO standards. To be meaningful the A must is used to introduce stability to generating sets operating in
Auto transformer starter Circuit breaker
be contained in LpA or LwA and with a proper description. parallel with one another.
Transformer switching arrangement to reduce voltage A protective device to automatically interrupt the flow
See also sound pressure v sound power.
applied to an electric motor during starting. of current in a circuit when the current level exceeds a
Double skin
certain value.
Deflection tolerance The extra layer inside a fuel tank and pipework to minimise
AVR droop
Term used in specifying vibration mounts, indicating the risk of potential leakage. Equally applies to any toxic
AVR voltage reference is reduced as load increases. Close-fit
capacity to accommodate ‘on site’ conditions. liquid around a generating set.
A generic term for an enclosure or canopy which is designed
to fit onto the base frame of the generating set; these may
be sound proofed or simply weather protected.
55 56
Dump line Full electronic authority digital engine control
Feed and return Impedance
Refers to the safeguarding method of using a pipe work Full authority digital engine control has no form of manual
Also known as flow and return pipes and refers to the Total of resistive, capacitive and inductive elements of
system to ‘dump’ fuel away from a day tank when there is override available, placing full authority over the operating
provision and route of suitable pipework to the bulk a circuit.
a potential fire risk. parameters of the engine in the hands of the computer.
fuel storage tank (see ‘bulk tank’), where the fuel can be
If a total FADEC failure occurs, the engine fails. If the engine
maintained and quality monitored. Particularly relevant Inrush current
Duty assist is controlled digitally and electronically but allows for
with the use of biofuels where there is a potential Initial instantaneous current drawn by transformers,
An arrangement where two (or more) generating sets are manual override, it is considered solely an EEC (electronic
degradation of quality if the fuel is stored for long periods capacitors or current-using equipment on the application
configured to provide mutual support in case of one piece engine control) or ECU (electronic control unit).
of time (see ‘Fuel polishing’). of a supply voltage. Causes of these high currents vary
failing to operate or needing assistance to achieve a required
with different types of equipment.
target: If one generating set fails to operate or cannot
Field
achieve a required target, the second (and subsequent) G59 protection
A permanent or electromagnet whose magnetic field Insulation
generating set will operate. An Energy Networks Association (ENA) document specifying
induces voltage in the armature coils of a generator. Non conductive material used between phases or phase
the connection and protection requirements for the
to earth to prevent current leakage. Generally classified
Duty standby connection of a generator, above 16amps, to the distribution
Fillpoint cabinet in terms of capability to withstand rises in temperatures or
An arrangement where two (or more) generating sets are network.
A cabinet, often wall mounted or free standing, with dielectric strength.
configured to provide mutual support in case of one piece
connections and equipment to allow remote filling of a fuel,
failing to operate: If one generating set fails to operate, Gas powered
or other fluid, tank. IP rating
the other one will operate. One unit is duty, the other(s) Gas fuelled generating set – differing gas types for differing
Ingress protection – degree of protection to ingress of
is standby to the duty unit. The terms duty assist and duty applications.
Fire rated enclosure/section building particles and moisture.
standby may be applied to other equipment, such as air
An enclosure constructed to meet a fire regulation i.e.
compressors and transfer pumps, in uses where additional Governor
BS476 four hour fire rating or offshore fire rating i.e. 60 Isochronous governor
resilience is important. A device on the engine for controlling fuel to the engine to
minutes integrity with a max temp rise from one side to Engine governor that maintains a set steady-state speed
maintain speed under varying load conditions or a pre-set
other of 140°C. without droop, regardless of the application of load.
speed droop from no-load to full load conditions (electronic
Earth fault or mechanical).
Fire protection systems
Failure of electrical insulation between live conductors
From a simple drop weight fire valve in the fuel line to full J 1939
and earth. May be considered for detection in “restricted” Grid codes
fire suppression systems; a system is in place to react in t The standard originally used for communication and
areas of a circuit or “unrestricted” i.e. occurrence of a An evolving set of international standards for all forms of
he even of a fire; cut off the flow of combustible material diagnostics among vehicle component and adopted widely
fault anywhere within a circuit. generators (alternators) which are aimed at better ensuring
(e.g. fuel) to an area or a machine and shut down the by diesel engine manufacturers due to the increasing
continuous and stable power supplies, and take into account
affected components or may suppress the fire with either adoption of the engine electronic control unit (ECU), and
Electronic governor the use of generation from renewable sources, as well as
water, foam or an inert gas. therefore found in a range of diesel-powered applications
Electronic device to control and maintain the speed achieving best transmission and distribution practices.
such as vehicles (on- and off-road), marine propulsion,
of an engine. Usually done by monitoring the output of
Free field measurement power generation and construction.
a tachogenerator or magnetic pick-up and feeding
Measurement of sound in an environment in which the effect
a proportional output to an actuator which controls the Hall effect sensor
of reflective boundaries can be considered negligible.
engine fuel supply. A method of measuring the strength of a magnetic field
Kilo-volt-ampere (k)VA
(by way of a transducer) that varies its output voltage in
Frequency 100VA. A term used for rating of an electrical circuit, which
Emission level stages response to a magnetic field by measuring the Hall effect,
The number of cycles of an alternating signal e.g. Electrical is the product of the circuit maximum current and voltage
European emission standards for new non-road diesel which is the small voltage that is produced when a flow of
current or sound in a given time such as cycles per second rating.
engines (fixed and variable speed). electrons interacts with a magnetic field. The CT’s (circuit
(Hz).
transformers) found in generating set control panels are
Kilo-volt-ampere reactive (kVAr)
Engine governing typical examples of sensors which reference the Hall effect.
Frequency regulation 100VAr. A term used for the rating of a purely inductive
Engine speed control (see governor) which may be
The degree of variation in steady state frequency of a or capacitive circuit, which is the product of the circuit
mechanical, hydraulic or electronic. Harmonics
generating set from no-load to fully loaded state. maximum current and voltage rating. Generally used in the
A component of a periodic signal with a frequency that is
context of that part of the generator output which is not
Engine starting a multiple of the frequency of the source signal.
Fuel lines giving true or active power, and that current which flows
12 or 24V electric, air, hydraulic, spring.
Pipelines from an engine to a fuel tank or from one fuel tank between generators in parallel.
Hertz
to another fuel tank.
Exciter The unit of frequency measurement equal to one cycle
Kilo-watt (kW)
A secondary generator or winding that provides DC per second.
Fuel polishing 1000 watts. Unit used for power rating of electrical devices.
power for excitation of the main field of a synchronous
The removal of water, sediment, non-combustible
AC generator. Hunting
particulate matter and microbial contamination to below Kilo-watt-hour
A term which can relate to speed or voltage and which
levels stated in ASTM D975 (standard specification for diesel 1000 watts-hours. The unit of electrical energy equal to the
Exhaust silencer occurs after a control function change, causing the
fuel oils) while resuspending combustible particulate matter use of one kW for the period of one hour.
Device to reduce noise level of engine exhaust system controlled element to continue to oscillate about the
to maintain ASTM standards for BTU value, lubricity and
(possibly indicatively referring to industrial or residential desired set value. Usually the result of insufficient damping
cetane number.
noise levels). in the control.

57 58
 Make before break Noise pollution
Load acceptance Parallel operation
An arrangement for electrical switchgear whereby two A term often used to refer to the inherent noise of any
Percentage of the rated set load that can be applied to a Operating two or more generating sets or generating sets
switching devices close to make a circuit in parallel before machines near to buildings and people which may require
generator set and is capable of accepting in one step and and the mains, networked together to supply a common
one switching device opens. This, as a term, often relates to treatment to reduce its effect, can also be a key design
recovering from within defined parameters. load (also see synchronisation).
parallel electrical power supplies, for arrangements where, consideration.
when changing from one power supply to another, there is
Load balancing Peak lopping/shaving
no interruption between supplies. Note that it is extremely Non-linear load
Common term used to describe best practice of balancing A term used to describe the use of a generating set system
important when considering parallel AC electrical supplies A load in which there is a non-linear relationship between
a load evenly across three phases where possible. to reduce load on the utility or mains supply, usually in
that consideration is made to ensure that the supplies are current and voltage. Commonly the result of electronic
times of peak demand. The generator may be used to
synchronised. This means making sure that voltages, phase switching during the cycle in the load circuits, typically in
Load bank maintain a fixed import quantity from the mains supply
angles and frequencies are matched. Attempted parallel most electronic controllers. See also harmonics.
Resistors and/or inductors that can be connected to a with the generator taking up the variations; alternatively
operation of supplies that are not synchronised can result in
generating set either for test purposes to simulate a real load the generating set system may be run at fixed load with
damage to equipment or risk personal injury. Normally closed/open contact
or to provide a method to absorb power where regenerative the mains supply taking up variations. The precise mode of
Description of the status of a relay contact when the relay
power may exceed the generator’s capability. Often mobile. operation should be agreed with the supply authority before
Main set breaker is de-energised.
commencing work.
The main breaker is the circuit breaker through which the
Load factor
full power of the generating set flows.
The ratio of average load to the generating set power rating. Pipe-In-Pipe
Octave band
Dual contained pipe system specifically designed for the
Mains breaker Frequency range where the highest frequency is double
Load step conveyance of fuel aimed to eliminate leaks. The interstitial
A circuit breaker that is usually positioned at the electricity the lowest, with eight bands 63Hz, 125Hz, 250Hz being used
Normally a percentage load applied to a generating set. space between the inner and outer pipe can be used with a
services intake of a premises and which may be interlocked most frequently to analyse and quantify sound.
leak detection system to guard against potential leaks in to
with a generator circuit breaker to form a changeover from
Lube oil make up system the environment (see double skin).
mains to generator power. Offset fill point
All engines consume lubricating oil when they run.
Remote or low-level fill points added to tanks to make
Therefore, the autonomy of an engine (time for which the PCL controls
Mechanical bridge the filling process easier. This is especially recommended
engine can run without requiring human intervention) is Programmable logic controller – a programmable hardware
A support for power cabling, fuel lines, exhaust, radiator etc. for tanks where direct-filling could cause safety issues
determined by how much oil in the engine is available to be control system which includes digital and analogue inputs
(see ‘fillpoint cabinet’).
consumed. To supplement this, a lube oil make up system and outputs.
Meg-ohm (MW)
can be added. This normally consists of a small lubricating
A unit used in defining the level of insulation in terms of its Ohm (Ω)
oil tank connected to the engine with a make up valve. Pole(s)
resistance to current leakage. The unit of electrical resistance; it is the ratio of 1 volt to
The make up valve provides a slow flow of oil to the engine Generally refers to the magnetic poles of field assembly of
1 amp.
to match the consumption of oil. It is important for a generator or motor. It can also refer to the electrodes of
Motoring
any engine that the autonomy of the lubricating oil system a DC battery or the number of contacts on a contactor or
This is the term applied when a generator remains Out-of-phase
matches or exceeds the autonomy of the fuel system. circuit breaker. Pole-pairs – four poles of the most common
connected to a network or other generators but its drive Referring to alternating currents or voltages of the same
generator designs, arranged in pairs at 120° to one another
engine fails to deliver power – the generating set continues frequency, which are not passing through their zero points
in the construction of a generator.
to run with the generator now driving the engine i.e. the at the same time.
Magnetic pick up
generator becomes a motor.
A device (hall effect sensor) that detects the speed of a Pole slip
Overload
prime mover, typically an engine or turbine. They are the A condition whereby a generator, or group of generators,
Moulded case circuit breaker (MCCB) Term referring to the amount by which an electrical circuit
communication link between the engine and an electronic terminal voltage angles (or phases) go past allowable
A circuit breaker which is enclosed in a plastic insulating is exceeding its rating.
governor control. The MPU is installed next to a flywheel ring (typically 90 or 180 degrees) limits with respect to the rest
case and which trips when the current exceeds a pre-
gear which is made of a material that reacts to a magnetic of the connected power system.
determined value for a given time. Overshoot aka overspeed
field. As each tooth of the ring gear passes within 0.75mm to
The amount by which voltage or frequency exceeds the
1.0mm of the MPU, the tooth interrupts the MPU’s magnetic Positive phase sequence current
nominal value following a load change.
field, and an alternating voltage is developed. The frequency Element of fault current vector in same phase sequence
Negative phase sequence current
of this voltage is translated by the speed control into a signal as the supply voltage.
In any three phase system, the currents that make up the
that accurately depicts the speed of the prime mover.
system can be resolved to positive, negative and zero phase
Power factor (Pf)
sequence phases. Thus the positive sequence components
In AC circuits, the power factor is the ratio of the real
produce a normal rotating field; the negative sequence
power flowing to a circuit (that is used to do work) and
components create a counter-rotating field and the zero
the apparent power that is available to do work in a circuit
sequence components produce an oscillating field that does
(the product of current and voltage). The power factor is
not rotate. Negative sequence components are an important
the dimensionless number unrecognised currently by
consideration of unbalanced ratings for generators as these
ISO standards.
cause heating, particularly in the field components.

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When all the power is reactive with no real power (usually Regenerative power Single bearing closed coupled Star – delta starter
inductive loads, such as motors) – the power factor is zero. See motoring. The AC generator has no bearing at the DE (i.e. engine Device for switching electric motor windings to reduce
When all the power is real power with no reactive power coupling) and its frame is tied to the engine flywheel starting current.
(resistive loads, such as heat elements) – the power factor Reverse power housing with a bolted adaptor.
is one. Power absorbed by a generator from a paralleled system Starting current
due to engine failure. Active power absorbed by a generator Solid state controls High current drawn by an electric motor during starting.
The generating set industry uses the convention of 0.8pf from the connected system. This may be another paralleled Electronic control (switching) devices e.g. transistors,
in three phase systems and 1.0pf, or unity, for single phase generator, the utility supply or possibly a motor such as a thyristors. Stator
systems. Figures between 0 to +1 are referred to as leading crane hoist that is being driven by the load. The stationary wound assembly of an AC generator or
power factors; figures between -1 to 0 are known as lagging Sound power v pressure levels exciter.
power factors. ROCOF The sound power level indicates the total acoustic energy
Rate of change of frequency. that a machine, (in our industry a generating set/s), radiates Sub-transient reactance
Prime power to its environment. The sound pressure level is a measure of Initial reactance of generator at instant of short circuit fault
The maximum power which a generating set is capable Root mean square the effect of the energy of an acoustic source (or a collection condition.
of delivering continuously whilst supplying a variable Mathematical term for establishing the “effective” of sources) and depends on the distance to the source(s)
load when operating for an unlimited number of hours (equivalent DC) value of the sinusoidal alternating quantity. and acoustic properties of the surroundings of that source. Surge
per year under the agreed operating conditions with the The sound power level of a machine is a fixed value, where A term applied to both current and voltage – it refers to an
maintenance intervals and procedures being carried out Rotor the sound pressure level always depends on position and exceptionally high increase in the quantity over a very short
as prescribed by the manufacturer. Rotating part of an electrical generator. environment. time period. Usually the result of load switching or lightning
strikes.
The permissible average power over 24 hours of operation The abbreviations for the figures are:
must not exceed 70% of the prime power agreed by the SCR (selective catalytic reduction) • SI (international system of units) only contains units Surge suppressor
engine manufacturer. As stated in BS ISO 8528. Selective catalytic reduction is a means of after treatment for pressure and power, not for levels. A general term used for a device to prevent externally
of turbo charged petrol, diesel and gas engine exhaust promoted voltage surges from destroying other devices.
gas emissions. They are used to remove nitrogen oxides Levels are described in ISO standards, using the following Commonly employed on the exciters of brushless generators
Radiator (NOx) and help reduce the amount of particulate matter in abbreviations or descriptors: to prevent rotating diode failure.
Typically, heat exchangers used to transfer thermal energy emissions which are known to directly damage health and • Sound pressure level – LpA
from one medium to another for the purpose of cooling convert the nitrox oxide to nitrogen and water vapour to • Sound power level – LwA Synchronisation
fluids flowing in circuits around an engine including the cause less harm to the environment. The act of matching the voltage magnitude, frequency
water jacket cooling the engine, a charge air circuit used The A relates to audio frequency referencing against an and zero crossing times (phase), of two alternating current
to cool directly the compressed air from an engine turbo Secondary contained ‘A-weighted’ table of logarithmic values where the decibel sources for the purposes of connecting them
chargers, prior to entry into the engine for combustion; A safeguarding method used to prevent unplanned releases values of sounds at low frequencies are reduced, compared in parallel.
a secondary water circuit on engines fitted with water of hazardous liquids such as diesel (see biodiesel) into with unweighted decibel values, in which no correction
cooled charge air coolers (WCCAC). uncontrolled areas, typically used when referring to fuel is made for audio frequency. As such in addition to the SI Synchronous reactance
pipe work (see binding). descriptors above it is accepted practice to find generating Measure of generator magnetic stiffness.
It must be remembered the radiator needs airflow across set sound attenuation shown as dBA or dB(A) however
the unit to get rid of the heat dissipated from the fluids. Self-excited generator without the distance from the sound sources being included
This airflow is generated from a fan which can be fitted A generator whose excitation system takes power from e.g. one meter, seven meters or sometimes 15 meters the Telephone influence factor
directly onto the engine, by one fitted onto the radiator its own output. value given is not an indication of the effect of the sound or Related to non sinusoidal voltage waveform and the
and driven from the engine via belts or ones fitted onto noise source. magnetic linkage between power and telephone cables,
an electric motor remote from the generating set. Separately excited generator it is a measure of the influence of the generated waveform
A generator whose excitation system takes power from a Sound power level on telephone operation.
Ratings separate source. Usually a secondary generator or exciter. Sound level in dB (or dBA) relative to reference power level
The output of a generating set relating to its use as defined in watts. Thermistor
in BS ISO 8528 as: Short term operating reserve A thermistor is a type of resistor whose resistance varies
• Continuous power (COP) Short term operating reserve is a service for the provision Sound pressure level significantly with temperature, more so than in standard
• Prime power (PRP) of additional active power from generation an/or demand Sound level in dB (or dBA) relative to reference pressure resistors. Thermistors are widely used as inrush current
• Limited-time running power (LTP) reduction. level in pascals. limiters, temperature sensors, self-resetting overcurrent
• Emergency standby power (ESP) protectors and self-regulating heating elements.
Shunt trip Speed droop
Radiometric This is a feature added to circuit breakers in order to Governor speed reference is reduced as load (or fuelling) Thermistors differ from a resistance temperature detectors
A term used in electronic circuits (or system) where the remotely trip the breaker from an externally derived signal; increases. See droop. (RTDs) in that the material used in a thermistor is generally
output has a direct proportional relationship to the input. such as a generator controller or switchgear control system. a ceramic or polymer, while RTDs use pure metals, such as
Star connection platinum. The temperature response is also different; RTDs
Reactance A connection of a three phase system or machine whereby are useful over larger temperature ranges, while thermistors
Steady state reaction to flow of AC current. the line voltage equals 1.73 times the phase voltage, and the typically achieve a higher precision within a limited
commonly connected phase ends form a neutral connection. temperature range, typically -90° to 130°C.

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Thermocouple Voltage regulation
Undershoot
Bi-metal junction producing signal voltage proportional to The allowed difference between maximum and minimum
Refers to the amount by which frequency or voltage drops
temperatures – used for temperature measurement. steady state voltage as a percentage of the nominal voltage.
below the nominal value as a result of load changes.

Thermostat Voltage regulator

Urea or DEF
Device which switches at a designed temperature – used to Device for maintaining the output voltage of a generator
Diesel exhaust fluid (DEF) – a solution of urea and deionised
control temperature of a medium e.g. air ambient, coolant between the allowed limits for varying load conditions.
water; commonly referred to as adblue. Standard for
temperature.
truck engines (variable speed) and may be specified
for certain generating set applications. Urea injection is
Time constant Watt
also used in power generation using natural gas engines
The recovery time of a system to a known point after a A unit of power.
where it is sometimes described as a CO-DINOx; the
step (load) change. Typically used in a generating set to
already cleaner exhaust gases from a lean burn natural
determine the response to step load and fault conditions.
gas engine are cleaned further to provide carbon dioxide
Zero sequence phase sequence current
which is of obvious use in, for example, the grower marker
Transformer Element of fault current vector with no phase sequence
(greenhouses) where a natural gas boiler is sometimes
May be alternating current or voltage related – the rotation. See also negative sequence.
replaced with a generating set. Such generating sets may
transformer is a device for changing the value of the
provide heat (CHP), electricity for lighting (see combined
quantity from one level to another. Zonal protection zone
heat and power) and well as CO2 that feeds plants.
Generally the term used for identification of areas of
Transient reactance hazardous environment – ATEX 137 Directive.
Transitional reactance of generator following sub transient
Varistor
stage of fault. The purpose of defining zones is to ensure employees
A resistance which has a significant change in value when a
and the public are protected from fires and explosion and
certain level of supply voltage is reached – used as a voltage
Transition fitting provide a level of risk assessment.
surge suppression.
Typically used to describe a polyethylene electro-fusion
or spigot jointed fitting with a steel thread or flanged Zone 0
Vibration mounts
connection. Giving a fast, simple method of transitioning to Explosive atmosphere with gas or vapour present
Often referred to as anti-vibration mounts to reduce (when
connections on tanks (see day tank and bulk tank), pumps, continuously for long periods or frequently due to
correctly selected) transmission of vibration from the
generators and other system apparatus. malfunctions, typically more than 1000 hours per year
generating set to the foundations. Types may be open or
– no motors allowed in Zone 0.
closed; media include steel spring or elastomeric e.g. rubber.
Triads
Half hour peaks of mains power demand which incur highest Zone 1
Volt
energy costs. Can be used to determine when local onsite Explosive gas or vapour likely to occur due to expected
The unit of electrical potential.
power generation should be used to power their loads. malfunctions, typically between 10 and 1000 hours per year
– flameproof or increased safety motors are allowed
Voltage dip
Twin bearing open coupled in Zone 1.
The temporary drop in generator voltage that occurs when
The AC generator has two bearings with shaft extension
a load is connected before the AVR control system responds
coupled to the engine flywheel without a mechanical tie Zone 2
and corrects it.
between the generator frame and the engine flywheel Explosive gas or vapour unlikely to occur, or if it does is
housing. likely to only be of short duration and not during normal
Volt free contact
duty, typically less than 10 hours per year – increased safety
A term used to describe a digital control signal used to
or non-sparking motors are allowed in Zone 2.
interface between systems. The indicating system opens
or closes a relay contact to provide a circuit. The “ends” of
Zone 20
the circuit are left available for the receiving system to use
Permanent presence of combustible dust-motors not
with a voltage of its choice. It is important when specifying
allowed.
a volt free contact that the intended voltage to be used on
the circuit is known to ensure that the circuit is rated for that
Zone 21
voltage.
Ignition proof motors approved and certified by a notified
body can be used – presence of combustible dust only by
Voltage drop
accident, but not during normal duty.
The voltage drop in a conductor (such as a cable) is the
result of the impedance of the cable which is effected by
Zone 22
the cable construction, length, installation method and
Dust ignition proof motors approved by a notified body or
temperature.
the manufacturer can be used.

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 Head Office
Cadder House
160 Clober Road
Milngavie
Glasgow G62 7LW

0141 956 7764

sales@dtgen.co.uk
www.dtgen.co.uk

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