CWA 14642:2003

SLOVENSKI STANDARD
01-november-2004
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CEN Workshop Agreement (CWA) - Electrical interface for domestic cogeneration -
Requirements for distribution network connection for micro cogeneration systems for
domestic use up to 16 A per phase in low-voltage distribution networks (230/400 V)
Ta slovenski standard je istoveten z: CWA 14642:2003
ICS:
27.010 Prenos energije in toplote na Energy and heat transfer
splošno engineering in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

CEN
CWA 14642
WORKSHOP
January 2003
AGREEMENT
ICS 27.010
English version
CEN Workshop Agreement (CWA) - Electrical interface for domestic
cogeneration - Requirements for distribution network connection for
micro cogeneration systems for domestic use up to 16 A per phase in
low-voltage distribution networks (230/400 V)
This CEN Workshop Agreement has been drafted and approved by a Workshop of representatives of interested parties, the constitution of
which is indicated in the foreword of this Workshop Agreement.
The formal process followed by the Workshop in the development of this Workshop Agreement has been endorsed by the National
Members of CEN but neither the National Members of CEN nor the CEN Management Centre can be held accountable for the technical
content of this CEN Workshop Agreement or possible conflicts with standards or legislation.
This CEN Workshop Agreement can in no way be held as being an official standard developed by CEN and its Members.
This CEN Workshop Agreement is publicly available as a reference document from the CEN Members National Standard Bodies.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2003 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members.
Ref. No. CWA 14642:2003  E
Content
1 Scope . 7
2 References. 8
3 Terms and definitions. 9
4 Safety requirements . 13
4.1 General . 13
4.1.1 The electrical installation. 13
4.1.2 Electrical equipment. 14
4.2 Connection of the appliance . 14
4.3 Connection of multiple micro-cogeneration appliances . 14
4.4 Protection functions of the electrical interface . 14
4.4.1 Over-/Under-frequency . 15
4.4.2 Over-/Under-voltage . 15
4.4.3 Over-current protection . 16
4.4.4 Other protection criteria . 16
4.5 Earthing. 17
4.6 Residual current protection. 17
4.7 Re-connection of the appliance . 17
4.8 Synchronisation. 17
5 Power quality. 17
5.1 Electromagnetic emission / immunity. 17
5.2 DC injection. 17
5.3 Power factor. 17
5.4 Voltage changes and flicker. 17
5.5 Voltage distortion . 18
6 Operation and safety of the appliance. 18
6.1 General . 18
6.2 Information plate and labelling. 18
6.3 Maintenance & routine testing . 19
7 Commissioning . 19
7.1 General . 19
7.2 Installation. 19
7.3 Notification procedure. 19
7.4 Decommission arrangements . 20
7.5 Replacement Arrangements . 20
8 Type testing and type certification. 20
8.1 Type testing. 20
8.2 Type certification micro-cogeneration appliance . 20
8.3 Type Certification of the electrical interface. 20
Annex 1: National requirements (2001 – informative) . 21
Austria. 21
Belgium . 21
France. 23
Germany . 24
Italy. 24
The Netherlands . 25
UK . 25
Annex 2: Notification sheets . 26
NOTIFICATION OF MICRO-COGENERATION INSTALLATION . 26
NOTIFICATION OF MICRO-COGENERATION APPLIANCE DECOMMISSIONING . 28
NOTIFICATION OF MICRO-COGENERATION APPLIANCE REPLACEMENT . 30
Annex 3: Abbreviations. 31
Annex 4: Bibliography. 32
Annex 5: CIRED summary of replies to Cen Workshop Agreement (informative) . 33
Foreword
This CEN Workshop Agreement has been drafted and approved by a Workshop of representatives of
interested parties in September 2002, the constitution of which was supported by CEN following the
public call for participation made in February 2001.
A list of the individuals and organizations which supported the technical consensus represented by the
CEN Workshop Agreement is available from the CEN Management Centre. These organizations were
drawn from the following economic sectors: manufacturers, testing and certification institutes,
distribution network operators (DNO), European Commission.
The formal process followed by the Workshop in the development of the CEN Workshop Agreement
has been endorsed by the National Members of CEN but neither the National Members of CEN nor the
CEN Management Centre can be held accountable for the technical content of the CEN Workshop
Agreement or possible conflict with standards or legislation. This CEN Workshop Agreement is not yet
a standard developed by CEN and its members.
The final review/endorsement round for this CWA was started in August 2002 and was successfully
closed in November 2002.The final text of this CWA was submitted to CEN for publication on 15
November 2002.
This CEN Workshop Agreement is publicly available as a reference document from the National
Members of CEN: AENOR, AFNOR, BSI, COSMT, DIN, DS, ELOT, IBN/BIN, IPQ, IST, MSA, NEN,
NSAI, NSF, ON, SEE, SIS, SFS, SNV, and UNI.
Comments or suggestions from the users of the CEN Workshop Agreement are welcome and should
be addressed to the CEN Management Centre
Introduction
CHP, Combined Heat and Power, or cogeneration is the simultaneous production of heat and
electricity. This proven technology produced in the year 2001 around 10% of Europe’s electricity and
heat requirements.
In recent years “micro-cogeneration” systems below 11 kVA have been developed. Within the micro-
cogeneration technology one can differentiate between domestic applications (e.g. for households)
and non-domestic applications (e.g. for hotels or swimming pools). Due to the lower running hours,
saving on domestic cogeneration is quite different from commercial micro-cogeneration. In order to
maximise the environmental benefits of domestic cogeneration these systems should be thermally led.
Micro-cogeneration is still an emerging technology and as such, lacks an appropriate standard for the
electrical interface. Existing standards are applicable to other parts of a micro-cogeneration system.
The technology for micro-cogeneration can be fuel cells, small gas engines, thermo-electric modules
and Stirling engines (possibly in conjunction with heat pumps or solar boilers).
The expected growth of micro-cogeneration will follow the normal market penetration of a new
technology. There is a need to address the initial market uptake for micro-cogeneration and this is the
purpose of this document.
Generally electrical networks have been developed to be operated in a centralised manner, where
large power plants produce electricity that is transported over long distances to provide power to many
customers. In such a system the power flows in only one direction: from the power station through the
network and to the customer.
With cogeneration systems the electricity can flow in two directions (from the cogeneration unit to the
network and from the network to the site where the cogeneration unit is located). This can be a
concern for the distribution utility , since the micro-cogeneration plant could be supplying energy into a
section of the DNOs network either under fault or normal operating conditions, this may create
problems for the safety of persons working on the network and the quality of the voltage supplied by
the network. A need for appropriate co-ordination and technical rules exists. The way this problem has
been dealt with so far varies from country to country. Whilst there are rules for distribution network
interconnection that are appropriate for larger scale cogeneration systems, they were not designed for
micro-cogeneration. In some European countries small-scale cogeneration systems can be connected
to the low voltage network. However, existing rules for small-scale less than 1 MWe maybe make it
onerous for the very small domestic micro-cogeneration systems to be operated.
If micro-cogeneration systems are not simple to connect and safe, they will never penetrate the
domestic market successfully. It is necessary to formulate technical specifications that solve all
technical issues at low costs. The specifications also need to be more straightforward and robust than
for industrial customers, because domestic consumers are not technically skilled and therefore need
more protection.
Widely accepted specifications will help to overcome the technical difficulties to connect micro-
cogeneration systems to electrical networks and to reduce the associated costs. Furthermore, it
should limit the risk of disputes between DNO and other parties (manufacturer, contractor and
customer). The intention of this document is not to change existing local standards or practices
immediately but is a recommendation of future good practice. It is built on growing experience of
micro-cogeneration in Europe.
LV electrical installations are covered by IEC 60364 and CLC HD 384. In some countries national or
local regulations apply, overriding these standards and the CWA.
This CEN Workshop Agreement applies to the electrical interface of micro-cogeneration systems for
domestic use, up to 16 A per phase. It deals with notification procedures as well as technical
specifications regarding safety and electrical co-ordination. Micro-cogeneration for domestic premises
will therefore require being a "fit and inform" process that meets all the necessary requirements of the
Distribution Network Operators.
Due to the practical difficulties as well as the lengthy procedure of developing an EN standard, it was
decided to start with a CEN Workshop Agreement and to use it as input for the normal standardization
process. As the CWA is a recommendation for good practice and not a standard national rules /
recommendations shall take priority over the recommendations in the CWA. It was agreed that CEN
will take over the Workshop Agreement, since CENELEC at that time did not have such a possibility.
Future development of the CWA towards an EN standard will be transferred to CENELEC.
———————
Utilities refers to private companies, national public or semi-public authorities responsible for the production and/or distribution
of electricity
CWA participants
Advantica Technologies Ltd United Kingdom
AEA Technology United Kingdom
Alstom Research and Technology Centre United Kingdom
BG Group United Kingdom
GASTEC N.V. The Netherlands
COGEN Europe European organisation
Danish Standards Association Denmark
DEFU Denmark
DVGW-EBI Germany
EA Technology Ltd United Kingdom
- Serviços de Energia Descentralizada, S.A. Portugal
ECOGEN
ecopower energy solutions AG Switzerland
EDF R&D / Normalisation France
Electricité de France – Gaz de France Services France
Electricity Association Services United Kingdom
ENEL Distribuzione Italy
EnergieNed The Netherlands
GASTEC Certification B.V. The Netherlands
GAZ De France France
International Conference on Electricity Distribution CIRED European organisation
Laborelec Belgium
Netherlands Standardization Institute NEN The Netherlands
NUON The Netherlands
RWE Net AG Germany
Sigma Elektroteknisk Norway
TÜV Rheinland Product Safety Germany
Université Catholique de Louvain, Unité TERM – Groupe Belgium
Energie Biomasse
Vaillant GmbH Germany
NOTE Participation does not mean that all listed participants have agreed and accepted the final version of the CWA in all
points as some may be in contradiction to existing national rules or guidelines (see Annex 1).
1 Scope
Micro-cogeneration is the generation of electricity and the recovery and use of the thermal energy
supplying the needs of domestic premises. This CEN Workshop Agreement covers the electrical
interface between the appliance and the low-voltage electrical network (nominal 230/400 V). Specific
elements like metering are not included. The intention of the CWA is to recommend future good
practice, noting that the CWA, local existing standards and practices may require modification in the
future due to larger market penetration and the associated return of experience.
NOTE The CWA reflects a pan-European view on best practice for the connection of micro-cogeneration; however it may not
be the most appropriate document for use in all countries and under all circumstances.
The following aspects are included in the scope:
• all technologies for micro-cogeneration are applicable;
• all generator types are applicable;
• the size is limited to a maximum of 16A per phase in a single low-voltage
installation (nominal 230/400V)
• both 3-phase and single-phase connections are applicable;
• connection is limited to low voltage networks;
• the electrical interface is the principal focus and this includes the method of
connection, the settings and protection requirements for connection, the operation
of the electrical interface under normal conditions, emergency shutdown,
distribution network-independent operation, start-up and distribution network
synchronisation;
• this document relates to the electrical interface only as existing standards and
directives apply to the other parts of the system;
• this document covers technical issues of connection.
NOTE The size is maybe increased up to 20 A (24 A) in accordance to the existing national standards in Germany, Austria,
Netherlands. It is permitted, in these countries, to feed a higher current than 16 A into the public grid. There are similar
requirements for the installation of special types of electrical appliances for domestic use (e.g. electrical water heater) with an
amperage higher than 16 A.
The following aspects are excluded from the scope:
• units exceeding nominal 230/400V;
• single phase units that exceed 16 A;
• multi phase units that exceed 16 A per phase;
• multiple units that exceed 16 A per phase in aggregate, for one installation;
• issues of revenue rebalancing, metering or other commercial matters;
• generators never to be connected to the supply networks.
The intention of the CWA is to insure that micro-cogeneration satisfies appropriate provisions for:
• safety of persons;
• information to electricians working inside the house
• voltage quality;
• reliability of supply;
• protection of the cogeneration unit.
Requirements for automatic disconnection and isolation regulations for safety purposes are included,
however the CWA does not cover the safety of DNO personnel or their contracted parties, as their
safety is a combination of the electrical conditions and working instructions, which is the responsibility
of the DNO. Labour safety of electricians working in the house is covered by other standards.
2 References
This CEN Workshop Agreement incorporates provisions from other publications in dated or undated
reference,. These references are cited at the appropriate places in the text and the publications are
listed hereafter. For dated references, subsequent amendments to or revisions of any of these
publications apply to this CWA only when incorporated in it by amendment or revision. For undated
references the latest edition of the publication referred to applies (including amendments).
Publication Ref doc Title
EN 50081-1 Electromagnetic compatibility (EMC) – Generic emission standard –
Part 1: residential, commercial and light industry
EN 50082-1 EMC - Generic immunity standard –
Part 1: residential, commercial and light industry
EN 50160 Voltage characteristics of electricity supplied by public distribution systems
EN 50178 Electronic equipment for use in power installations
EN 55014-1 CISPR 14-1 Electromagnetic compatibility – Requirements for household appliances, electric tools
and similar apparatus –
Part 1: Emission – Product family standard
EN 55014-2 CISPR 14-2 EMC – Requirements for household appliances, electric tools and similar apparatus –
Part 2: Immunity – Product family standard
EN 55022 CISPR 22 Information technology equipment – Radio disturbance characteristics – Limits and
methods of measurement
EN 60335-1 Safety of household and similar electrical appliances –
Part 1: General requirements
EN 60730 IEC 60730 Automatic electrical controls for household and similar use
EN 61000-3-2 IEC 61000-3-2 EMC – Part 3-2: Limits -
Limits for harmonic current emissions (equipment input current up to and including 16
A per phase)
EN 61000-3-3 IEC 61000-3-3 EMC - Part 3-3: Limits -
Limitation of voltage fluctuations and flicker in low-voltage supply systems for
equipment with rated current up to 16 A
IEC 61000-6-1 Electromagnetic compatibility (EMC) - Part 6: Generic standards - Section 1: Immunity
for residential, commercial and light-industrial environments
IEC 61000-6-3 Electromagnetic compatibility (EMC) - Part 6: Generic standards - Section 3: Emission
standard for residential, commercial and light-industrial environments
IEC 61009-1 Residual current operated circuit-breakers with integral over-current protection for
household and similar uses (RCBOs) - Part 1: General rules
HD 384 IEC 60364 Electrical installations of buildings
modified
IEC 60050 International Electrotechnical Vocabulary (IEV)
- 151: Electrical and magnetic devices
- 195: Earthing and protection against electrical shock
- 411: Rotating machinery
- 442: Electrical accessories
- 448: Power system protection
- 601: Generation, transmission and distribution of electricity - General
- 603: Generation, transmission and distribution of electricity
– Power systems planning and management
- 811: Electric traction
- 826: Electric installations of buildings
IEC 61140 Protection against electric shock – Common aspects for installation and equipment
3 Terms and definitions
For the purpose of this CWA, the following definitions apply.
Appliance
An assembly of components to fulfil one or more functions and provided with a cover to protect the
user from hazards and the assembly from damage. To exchange energy, information, etc., an
appliance has connecting electric wires, fuels supply, water pipes and flue gas pipes etc.
For a micro-cogeneration appliance, the typical assembly consists of

For gas engines and Stirling engines, an engine to convert fuel to mechanical power,
mechanical to electrical conversion (generator, alternator, and/or inverter), electrical interface
(synchronisation device, inverter, interface protection).

For fuel cells, typical systems consist of a chemical-to-electrical power conversion, an inverter
and electrical interface.
The electrical interface monitoring- and control-functions may be incorporated into the micro-
cogeneration unit, or may be fitted as a discrete remotely mounted device. In either case the micro-
cogeneration unit and its electrical interface comprise the appliance and must contain also an isolating
switch.
Micro Cogeneration System Flue Gas
Heat
Electrical Alternator Prime Mover
Output
Electrical connection
Interface
Appliance
Fuel Supply
Figure 1:
Micro-cogeneration system (example)
Appliance fault current
The contribution from the appliance to the current flowing to the fault
Automatic reclosing equipment
Automatic equipment that is designed to initiate the reclosing of circuit-breaker(s) after operation of the
protection on the associated circuit
Certified appliance
An appliance that meets the product certification requirements
Clearing time
The clearing time is the time between the start of an abnormal condition and the micro-cogeneration
unit ceasing to energise the installation or network
———————
where possible IEC Multilingual Dictionary (on CD) is used
Cogeneration (CHP: combined heat and power)
The generation of electricity by an energy conversion system and the concurrent use of the associated
thermal energy from the conversion system as an auxiliary energy source
Commissioning
The process by which a power plant, apparatus, or building is approved for operation based on
observed or measured operation that meets design specifications
Contracted person
The person who holds the contract for electricity connection at the house, where the micro-
cogeneration appliance is installed
Decommissioning
The process of removing an appliance, apparatus, equipment, building, or facility from operation
Decoupling protection
Comprises all functions including loss of mains protection
Disconnection (automatic)
The automatic disconnection of the supply from the installation, or a discrete section of it
Distribution Network (DN)
The electrical network transporting electricity in medium and low voltages between the transmission
network and the connected customer
Distribution Network Operator (DNO)
The company responsible for operating, maintaining, managing connections and investing in the
distribution network
Earth fault
The occurrence of a conductive path between a live conductor and the Earth
Domestic electrical installation
An assembly of electrical equipment that is used inside the domestic premises for the distribution
and/or use of electric energy except the cogeneration appliance itself (fuse – meter - switchboard –
installation)
The following diagram is for illustration only
Electrical Installation
Micro Cogeneration
Appliance
kWh
Figure 2:
Domestic electrical installation together with the micro-cogeneration appliance (example).
Electrical interface
Those parts of a cogeneration unit’s software and hardware that interact with the electrical installation
and network through the terminals of the unit
Electricity exports
The electric energy generated in an electrical installation and flowing to the distribution network
Electricity supply system
All installations and plants provided for the purpose of generating, transmitting and distributing
electricity
Fuel cell
An electrochemical device that converts chemical energy directly into heat and electricity
Gas engine
An internal combustion engine modified or specifically designed to run on gaseous fuel
Generating unit
A device for transforming mechanical, thermal or chemical energy into electricity
Installation (of the appliance)
The placement and connection of a micro-cogeneration appliance
Internal Combustion Engine
An engine in which combustion of the fuel takes place in a confined space, providing expanding gases
that are used directly to provide mechanical power
Inverter
A static converter for the conversion of direct current to alternating current
Island (in a power system)
A portion of a power system, that is disconnected from the remainder of the system, but remains
energized
Islanding, intended
This occurs when the installation is operated intentionally to supply electricity to the consumer when
the network is temporarily unavailable
Islanding, unintended
This occurs when the network fails and the unit continues to operate in a grid connected manner
Islanding (network splitting)
The process whereby a power system is split into two or more islands
NOTE :– Islanding is either a deliberate emergency measure, or the result of automatic protection or control action, or the result
of human error
Isolation
The disconnection of all phases and neutral from an apparatus for safety and accessibility reasons.
Once the appliance has been isolated and shut down it can be safely accessed
Kinematic Stirling Engines
In this design of engine, the piston(s) are driven through connecting rods and a crankshaft, swash
plate or other means. [Stirling Engines Colin D West]
Labelling
The use of appropriate safety notices and information on the appliance and other relevant places
Linear electric generator
A linear motion electromagnetic device that transforms short-stoke oscillatory motion mechanical
energy into single-phase ac electrical energy
Linear Free Piston Stirling Engine (LFPSE)
A Stirling cycle engine with a “free” mechanical piston and a sprung piston forming a dynamic, linear
resonant system operating at its natural frequency
Loss of mains protection
See protection against islanding
Low Voltage
The set of voltage levels used for the distribution of electricity and whose upper limit is generally
accepted to be 1000 V a.c., but for the purposes of this document LV means 230/400 V.
Moulded case circuit breaker (MCCB)
A circuit breaker completely enclosed within a ruggedly constructed moulded case of insulating
material. With a current/time-based trip mechanism and manual reset. Gives an automatic protection
against short-circuits and overload currents.
Notification
The process of informing the DNO of an installation of a micro-cogeneration system, or its removal
Origin of an electrical installation
The point at which electric energy is delivered to an electrical installation from the appliance
Power factor
The COSIN of active power to the apparent power
NOTE In the case of a converter, the two quantities apply to the same a.c. side.
Power system fault
A power system abnormality which involves, or is the result of, failure of a primary system circuit or
item of primary system plant or equipment or apparatus and which normaIly requires the immediate
disconnection of the faulty circuit, plant or equipment or apparatus from the power system by the
tripping of the appropriate circuit-breakers
Product certification
The whole process including prototype examination and production surveillance that results in the
notification by a notified body that the confidence is justified and that a clearly defined product meets
the requirements concerned, as laid down in the approval requirements
Protection
The electrical protection required to ensure that the appliance is disconnected for any event that could
impair the integrity or degrade the safety of the Distribution Network.
NOTE
- The term “‘protection” is a generic term for protection equipment or protection systems;
- The term “protection” may be used to describe the protection of a complete power system or the protection of individual plant
items in a power system e.g. transformer protection, line protection, generator protection;
- Protection does not include items of power system plant provided, for example, to limit over-voltages on the power system.
However, it includes items provided to control the power system voltage or frequency deviations such as automatic reactor
switching, load-shedding, etc
Protection equipment
Equipment incorporating one or more protection devices and, if necessary, logic elements intended to
perform one or more specified protection functions
Protection against islanding
Provisions for detecting faults or other abnormal conditions in the electricity supply system and for
separating the distributed generating units from the system, in order to avoid islanding
Prospective short circuit current
The electric current that would flow if the short-circuit were replaced by an ideal connection of
negligible impedance without any change of the supply
Reconnection
When the appliance connects again to the electricity network after a period of disconnection
ROCOF
Rate of change of frequency – a method of detecting islanding. Other methods could include
frequency shift, vector shift or impedance variation
Residual current
The r.m.s. value of the vector sum of the currents flowing through all live conductors and neutral of a
circuit at a given point of the electrical installation
Residual current protection
A system to detect residual current and protect against earth leakage
Short-circuit
Accidental or intentional conductive path between two or more conductive parts forcing the electric
potential differences between these conductive parts to be equal or close to zero
Short circuit current
The electric current in a given short-circuit
Stirling Engine
A mechanical device which operates in a closed regenerative thermodynamic cycle with cyclic
compression and expansion of the working fluid at different temperature levels, leading to a net
conversion of heat to work or vice-versa
Synchronous machine
An alternating current machine in which the frequency of the generated voltages and the speed of the
machine are in a constant ratio
Type Testing
The Type Examination procedure requires that representative samples of a mass produced product
are evaluated and/or tested to the relevant requirements and/or Standards to ensure conformity with
the applicable Directives. The testing may be required to be carried out by a Notified Body for some
Directives. If the product is found to be satisfactory, a Type Examination Certificate will be issued.
Type certification
The procedure required for gaining approval for a mass produced product. Once approved the
manufacturer may affix the “CE” mark. This procedure includes Type Examination and Production
Surveillance. In some cases a Notified Body is required evaluate the methods of production and/or
products produced to ensure that these are consistent with the sample subjected to Type Examination.
4 Safety requirements
4.1 General
For general requirements see also EN 61140 : protection against electric shock – common
aspects for installation and equipment.
4.1.1 The electrical installation
Low voltage electrical installations shall comply with national and local regulation whether the
installation is supplied by cogeneration running in parallel with the distribution network, solely
by the supply network or islanded. Additionally, the interface provisions laid down in this CWA
apply where micro-cogeneration systems are connected either directly to the electricity supply
system or to an electrical installation being supplied by the electricity supply system.
Particular attention is needed when cogeneration is added to an existing installation.
NOTE The CWA mainly refers to IEC 60364 -5 "Selection and erection of electrical equipment", clause 551 "Low-voltage
generating set" and focuses to the clauses 551.1 to 551.7, (scope, general requirements, protection against indirect contact,
protection against over-current, additional requirements….switched., and additional requirements…parallel ….)
Regarding to the scope of this CWA, some types of appliances mentioned in these clauses are excluded such as:
- photovoltaic cells (60364 - 511.1.1);
- electrochemical accumulators (60364 - 511.1.1):
- temporary and portable systems (60364 - 511.1.1);
- not permanently fixed systems (60364 - 511.1.4);
- systems for extra low voltage (60364 - 511.3.1) 230/400 volt systems only
Regarding to 551.7.1 and 551.7.2: Consulting the DNO is not compulsory.
This CWA proposes a "Fit and inform" situation, due to the small capacity and type certification.
4.1.1.1 Maintenance
The contracted person shall properly maintain the electrical installation. These obligations do
not change after the installation of the micro-cogeneration appliance.
4.1.1.2 Selectivity
Electrical installations and their components should be selectively protected, bearing in mind
the protection provided by the DNO to the connection of the electrical installation or to the DN.
4.1.1.3 Protection device of DNO
When dimensioning the electrical installation, account needs to be taken of the protection
device installed by the DNO.
4.1.2 Electrical equipment
EN 60730 ‘Automatic electrical controls for household and similar use, Part 1: General
requirements’ and EN 60335-1 ‘Safety of household and similar electric appliances – Part 1:
General requirements’ are recommended to be applied. These standards deal with electrical
safety to the person. The important items are earthing, electrical insulation etc.
4.2 Connection of the appliance
The unit shall be connected through its own electricity supply system interface. The connection
shall be protected for overloads and short circuits fed from the network by the suitable means
of fuses or MCCBs.
4.3 Connection of multiple micro-cogeneration appliances
In a single domestic premise each individual micro-cogeneration appliance shall have its own
electricity supply system interface.
4.4 Protection functions of the electrical interface
Protection settings will need to be agreed nationally. The protection settings shown in the
CWA are intended to be indicative of the type and range of settings that may be required.
If no national settings are available, then the proposed settings below shall be used.
The protection shall serve the purpose of:
- safety of persons;
- voltage quality;
- security of supply;
- protection of the micro-cogeneration appliance.
The same protective measure could serve several purposes.
The protective system disconnects the appliance at the point of the electrical interface through
various criteria derived mainly from measurements of the voltage, the current and the
frequency.
In case of automatic safety switching some countries require two switching devices in series.
At least one of them shall be an all-pole load-breaker ensuring a galvanic isolation.
Characteristics given in 4.4.1 to 4.8 together with national settings given in Annex 1 fulfil the
purposes of the protection.
The protective system should be insensitive to the normal voltage and frequency variation in
the DN. That means, that the appliance shall stay connected in situations with under- and
over-voltages and under- and over-frequencies unless the appliance is disconnected by the
protective functions specified in the following clauses.
NOTE This is to avoid cascade loss of generation.
4.4.1 Over-/Under-frequency
The appliance shall have a protection from over- and under-frequency. If no national
requirements are available the levels in 4.4.1.1 – 4.4.1.2 shall apply. Only one protection
setting per country is allowed.
4.4.1.1 Over-frequency
Protection for over-frequency shall have a setting of not more than 51 Hz and a disconnection
time of not more than 200 ms.
NOTE
- a narrow frequency setting increases the probability of detecting islanding. However, the setting should not be too narrow, as
the frequency may deviate more than normal from 50 Hz in abnormal situations.
- if islanding is detected by another protective method, as for example ROCOF, there is no need for a narrow frequency
setting;
- EN 50160 prescribes that the frequency shall be within the range of 49,5-50,5 Hz in 99,5% of a year and within the range 47-
52 Hz during 100% of the time. For systems with no synchronous connection to an interconnected system the frequency shall
be within the range of 49-51 Hz in 99,5% of the year.
- machine protection is not under consideration here (synchronous machines may require faster response times).
4.4.1.2 Under-frequency
Protection for under-frequency shall have a setting of not less than 47 Hz and a disconnection
time of not more than 200 ms.
NOTE
- all countries except one require a protection against under-frequency. The required frequency setting varies from 47 to 49,7
Hz.
- a narrow frequency setting increases the probability of detecting islanding. However, the micro-cogeneration units must
contribute to the production of electricity in case of system faults leading to a drop in frequency. This is probably the reason
why most of the countries require a setting of 47 Hz.
- Machine protection is not under consideration here (synchronous machines may require faster response times).
4.4.2 Over-/Under-voltage
The micro-cogeneration appliance shall have voltage protection to protect appliance, the
network and the other customers connected in the neighbourhood from over- and under-
voltage and to detect islanding.
If no national requirements are available the levels in 4.4.2.1 – 4.4.2.2 shall apply. Only one
protection setting per country is allowed.
4.4.2.1 Over-voltage
Over-voltage protection is required.
The voltage setting shall be 230 V +6%. If this value is exceeded for one minute continuously,
the protection must disconnect the appliance. These settings will also protect micro-
cogeneration units against unwanted tripping caused by switching operations in the electricity
supply system and associated temporary over-voltages.
Countries may choose higher settings for network operational reasons.
Micro-cogeneration units can generate over-voltages after the formation of an island. As an
over-voltage can develop very fast, a second over-voltage protection function shall initiate the
disconnection of a micro-cogeneration unit no later than 200 ms after 115 % of the nominal
voltage is exceeded.
NOTE
- Taking into account that the voltage can go beyond the voltage setting before a micro-cogeneration unit has disconnected, a
setting of not more than 115% is recommended;
- The shortest possible clearing time depends on the time needed to have a reliable measurement and the time needed by the
protection to disconnect a micro-cogeneration unit. It is proposed to have a clearing time of 200 ms (10 periods).
4.4.2.2 Under-voltage
Under-voltage protection is required.
If a dedicated method for the detection of islanding is not used, the under-voltage protection
shall assist in the detection of islanding.
NOTE The required voltage settings may differ between countries.
The voltage setting shall be 230 V - 15 %. If the voltage drops below this limit for 2 seconds,
the protection must disconnect the appliance to prevent unintended islanding.
Shorter clearing times may be required for some micro-cogeneration units that do not
withstand out of phase switching. The size of the voltage dip and the clearing time are
dependant on the machine characteristics.
Micro-cogeneration units should not disconnect in the case of short voltage dips caused by
faults in the supply system. A short clearing of < 200 ms will be required if the voltage drops
below 70 %.
NOTE A synchronous generator should be equipped with a device that will effect a separation within 200 ms from the DN in the
event of voltage dropping in one or more phases to 70% of the nominal value, unless more rapid disconnection appears
necessary on the basis of a calculation of the critical short-circuit time for the machine.
4.4.3 Over-
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