Section
5 System components
5.1 Source of electrical power
5.1.6 Converters within power sources are to comply with the requirements of
Vol 2, Pt 9, Ch 3, 7.2 Semiconductor converters and the
following requirements:
- Converters are to be selected to withstand the voltage
ripple levels present on the distribution system. For every system, the
following voltage parameters are to be defined:
- maximum non-repetitive peak;
- maximum repetitive peak; and
- maximum repetitive peak-to-peak.
- Where pulse width modulation converters are to be used, the
voltage rate of rise times are to be determined, the results recorded and
submitted to LR. Rotating machinery, surge protective devices, cable insulation
and motor windings are to be designed accordingly.
- Converters may be of conversion type a.c./a.c., d.c./a.c.,
a.c./d.c., d.c./d.c., and can be of the controlled (e.g. active front end (AFE))
or non-controlled type (e.g. diode supply unit (DSU)).
- Converters are to be provided with visual status indication
at their associated control stations to include, but not be limited to:
- power available at the input;
- power at output;
- temperature; and
- overload.
If certain indicators and
alerts are not applicable, sufficient evidence to support the claim
is to be submitted for consideration by LR. Additional indicators,
alerts and shutdowns may be necessary as determined through the
system Failure Modes and Effects Analysis (FMEA) required by Vol 3, Pt 1, Ch 6, 7.10 System Failure Modes and Effects Analysis (FMEA).
- Converters supplying electrical power to the distribution
system and consumers are to be capable of delivering the required currents for
the time required to enable current-time discrimination of protective devices to
operate. The electrical output of the converter is to be automatically restored
following fault clearance.
- Converter software is to meet the requirements of Vol 2, Pt 9, Ch 8 Programmable Electronic Systems.
- Converters are to be capable of handling voltage and current
spikes from the distribution system under all normal and reasonably foreseeable
abnormal conditions without sustaining any damage or tripping.
- Converters supplying essential services are to automatically
restart and connect to the distribution system after a blackout as specified in
Vol 2, Pt 9, Ch 2, 4.2 Number and rating of generators and converting equipment.
- Where converters are equipped with internal capacitors which
can contribute significantly to the short-circuit level of the system, the
contribution is to be included in the design of the protection and distribution
system.
- The risk of converter component damage due to inrush
currents is to be minimised by appropriate management of these currents during
transient events and after short circuit.
- Where capacitors are connected to a converter output, the
output is to be charged by the converter or by external chargers to a level
which will minimise the risk of damage to the capacitors before connecting them
to the distribution system.
- Converters arranged to operate in parallel are to be capable
of stable load sharing up to maximum continuous load and inclusive of any
temporary overloads within their design rating.
- Where converters are arranged to provide protection against
electrical faults a disconnector or switch disconnector is to be provided to
enable safe isolation of the converter from its incoming supplies.
- Converters are to be protected from permanent physical
damage as a result of short circuits or overload currents on their input and
output terminals.
- Converters are to have a ride-through capability to manage
system transients including the effects of fault clearance in the distribution
system that is consistent with the dependability requirements of the
system.
- Converters are to be provided with appropriate filters to
ensure the required quality of power supply at both their input and output. In
the event of filter circuit failure, continued safe operation of the hybrid
electrical power system is to be possible by following specified procedures as
described in operation procedures. These procedures are to include any
operational limitations, and they are to be kept on board, maintained in
accordance with Vol 3, Pt 1, Ch 6, 7.1 General 7.1.3 and made available
to the Surveyor on request.
5.2 Store of electrical energy
5.2.1 Functional requirements: To provide sufficient stored electrical energy as a
component of the main source of power to supply services during normal and
reasonably foreseeable abnormal and emergency conditions.
5.2.4 For consideration as a component of the main source of power on a ship with a
specified service notation and subject to approval of the Naval Administration a
store of electrical energy is to:
- Comply with Vol 3, Pt 1, Ch 6, 4.4 Main source of electrical power;
- Have a minimum capacity at any stage of its lifecycle
sufficient for its contribution to the main source of power that is necessary to
achieve the specified service requirements;
- Be provided via energy management functionality with remote
indication of state of charge (available capacity in a store expressed as a
percentage of rated capacity) and state of health (general condition of a store
expressed as a percentage of its ability to deliver the specified performance
compared with that of a new store);
- Have a primary purpose of supplying the ship’s main power
demand. Details of any secondary purpose including but not limited to optimising
performance (e.g. load smoothing, peak shaving), improving stability (e.g.
dynamic response) or providing transitional power are to be provided to LR;
and
- Be capable of being restored from a dead-ship condition with
no dependence on other systems or electrical supplies. Details of alternative
arrangements may be submitted for consideration by LR.
5.2.5 For consideration as an additional source of power a store of electrical energy is
to:
- Comply with Vol 3, Pt 1, Ch 6, 4.4 Main source of electrical power 4.4.2;
- Be provided via energy management functionality with remote
indication of state of charge (available capacity in a store expressed as a
percentage of rated capacity) and state of health (general condition of a store
expressed as a percentage of its ability to deliver the specified performance
compared with that of a new store); and
- Have a primary purpose of supplying the ship’s main power
demand. Details of any secondary purpose including but not limited to optimising
performance (e.g. load smoothing, peak shaving), improving stability (e.g.
dynamic response) or providing transitional power are to be provided to LR.
5.2.7 Electrical energy storage devices connected to and charged by the distribution system
are to be protected against the defined effects of electrical faults in the
system.
5.2.8 Energy stores connected to and charged by the distribution system are to be so
located and provided with arrangements allowing for the safe isolation of their
terminals and the reduction of voltages to a safe level during maintenance or
provided with alternative arrangements providing an equivalent level of safety which
will be subject to special consideration.
5.2.9 Energy stores are to be connected to the distribution system by protection devices
which include but are not limited to overcurrent and short circuit protection. The
protective devices used are to be selective, ensuring faults are not transmitted
further, independent of the direction of current flow.
5.3 Consumer of electrical power
5.3.1 Functional requirements: To convert electrical power supplied from the hybrid power
generation and distribution system into useful work.
5.3.4 Where a converter is arranged to step down voltage to provide a lower voltage supply
to consumers than that of the power system then arrangements are to be provided to
ensure the lower voltage distribution consumers are not subjected to voltage
variations, including fast transients, outside their safe operating regions.
5.3.5 Consumers employing loads characterised by constant power
characteristics connected to the distribution system through a converter are to be
evaluated with respect to ensuring the stability of the power system as part of the
power system analysis detailed in Vol 3, Pt 1, Ch 6, 7.7 Power system analysis.
5.4 Combined sources of electrical power, stores of electrical energy and consumers of electrical power
5.4.1 Functional requirements: To provide the combined functional requirements of each of
the elements (sources, stores, consumers) from which the combination is
constructed.
5.5 Distribution system
5.5.1 Functional requirements:
- To provide a dependable interconnection between sources,
stores and consumers of electrical power; and
- To distribute electrical power safely to consumers.
5.5.2 Arrangements for isolation and switching are to be provided which are to enable safe
isolation of faults and for maintenance.
5.5.3 Distribution systems supplying consumers through converters are to provide galvanic
isolation and ground separation.
5.5.4 In addition to the requirements of Vol 2, Pt 9, Ch 3, 4.3 Isolation and switching, systems are to comply with the requirements of Vol 3, Pt 1, Ch 6, 5.5 Distribution system 5.5.5 to
Vol 3, Pt 1, Ch 6, 5.5 Distribution system 5.5.13.
5.5.5 Where consumers are supplied via converters which are connected to both sides of a
distribution system that is capable of being split, arrangements are to be provided
to eliminate the risk of current being supplied back to the distribution system for
example through flyback diodes.
5.5.6 Converters connecting sources, stores and consumers to the distribution system are to
facilitate connection and removal of the sources, stores and consumers in a stable
manner with the electrical power system in operation.
5.5.7 Converters are to be designed to prevent damage to the converter when switching under
load.
5.5.8 Where essential services are required to be duplicated, these are to be served by
individual circuits, separated in their switchboard or section board and throughout
their length as widely as is practicable without the use of common feeders,
protective devices, control circuits or controlgear assemblies, so that any single
fault will not cause the loss of both services.
5.5.9 The distribution system is to be split into at least two independent systems each
capable of independent operation or is to be separated by protection devices that
are selective, ensuring faults are not transmitted further, and operate independent
of the direction of current flow.
5.5.10 The distribution system is to be protected against electrical faults
including short circuit, overload, earth fault, differential current, under/over
voltage, under/over frequency, power quality, current and voltage imbalance, arc
fault in compliance with the relevant requirements of Vol 2, Pt 9, Ch 4, 4 System design - protection and Vol 3, Pt 1, Ch 6, 5.5 Distribution system 5.5.2 to Vol 3, Pt 1, Ch 6, 5.5 Distribution system 5.5.16.
5.5.11 Active components may be used for the limitation of fault currents
subject to verification in a real environment of the performance of the component
under all normal and reasonably foreseeable abnormal operating and fault conditions
and subject to establishment of effective surveillance and periodic test procedures
during operation and maintenance in the ship’s Operating Manuals to verify the
component is capable of performing its intended function. An isolation device is to
be provided within the component and this is to be tripped automatically in the
event of the component operating. A risk assessment of the component is to be
undertaken to a recognised standard that is acceptable to LR (e.g. ISO 31010,
Risk management – Risk assessment techniques) and in accordance with LR's
ShipRight Procedure Risk Based Certification (RBC).
5.5.12 Where energy management functionality provides protection against incorrect or
unexpected energy flows between the sources, stores and consumers forming part of
the hybrid electrical power system the sensors used for this purpose in the
distribution system are to be independent of those used for control, monitoring and
safety systems.
5.5.13 Where a bi-directional flow of power may occur, the distribution system is to
withstand the power variations being introduced. The level of bi-directional flow
allowed is to be specified by the system designer.
5.5.14 For Hybrid Power (+) notation facilities are to be provided for automatic
detection of the location of insulation breakdown with respect to earth of equipment
and distribution systems to a level determined by the integrator consistent with the
system’s dependability targets and agreed with the designers and Owners.
5.5.17 Where fuses are implemented to limit the fault current in the converter,
the activation of the protection is not to influence redundant consumers or cause
loss of other single consumers as required by Vol 2, Pt 9, Ch 3, 4.2 Essential services.
5.5.18 Fuses used to protect distribution converters are to be of the bolted type. Where
alternative arrangements are proposed, it is to be demonstrated that protection
system’s selectivity is not adversely affected as a result of an increased
connection resistance.
5.5.19 For each section of a d.c. bus there is to be at least one voltmeter per section. An
ammeter is to be provided for each converter supplying a d.c. bus. Similar
arrangements are to be provided for screen-based displays.
5.5.21 Power quality assessments are to consider the detection and impacts of circulating
currents such as may exist through capacitive coupling in semiconductor
converters.
5.5.22 Constant current distribution systems will be subject to special consideration and
are not covered by these Rules.
5.5.23 For Hybrid Power (+) notation warnings of degrading power quality
are to be provided and in the event of power quality exceeding prescribed limits
automatic isolation and reconfiguration of the power system is to occur as agreed
between the designers and Owners.
5.6 Energy management
5.6.1 Functional requirements:
- To ensure that sufficient energy is available to satisfy the
main power demand under all foreseeable operational conditions.
- To inform Operators as soon as reasonably practicable of
deviations from normal operation of the hybrid electrical power system under all
normal and reasonably foreseeable abnormal operational conditions.
- To initiate immediate corrective action on detection of
component faults in the hybrid electrical power system that present a danger,
reducing the risk to a level that is acceptable to LR.
- To provide functionality beyond the scope of conventional
power management that is necessary for the control, monitoring, protection and
dependability of the hybrid electrical power system.
5.6.4 Loss of energy management functionality is not to compromise the supply
of main power, the safety of the ship, the hybrid electrical power system or its
components.
5.6.5 Energy management functionality is to include, but not be limited to, the
following:
- Control (of the complete system and of each of its
sub-systems):
- Hybrid electrical power system operating mode
selection and transition;
- Connection and disconnection of sources, stores and
consumers to the distribution system in response to operating conditions
and prevailing loads;
- Connection and disconnection of distribution system
sections;
- Load allocation to and sharing between sources;
- Load restriction of consumers;
- Energy flow management;
- Distribution system a.c. voltage and frequency and
d.c. voltage; and
- Control functions required by sources, stores,
consumers or distribution system that are necessary for their operation
under all reasonably foreseeable normal, abnormal and fault
conditions.
- Alarm and monitoring:
- Mode transition status;
- Connection status of sources, stores, consumers and
distribution system sections;
- Energy flows within the hybrid electrical power
system and between its constituent parts;
- Power quality as detailed in Vol 3, Pt 1, Ch 6, 6.2 Power quality and stability 6.2.2; and
- For stores, state of charge and state of health as
defined in Vol 3, Pt 1, Ch 6, 5.2 Store of electrical energy 5.2.4 and Vol 3, Pt 1, Ch 6, 5.2 Store of electrical energy 5.2.5.
- Protection and safety:
- Blackout prevention;
- Blackout recovery;
- Detection of abnormal or unexpected energy flow as
described in Vol 3, Pt 1, Ch 6, 5.5 Distribution system 5.5.12; and
- Safety functions required by sources, stores,
consumers or distribution system that are necessary for their safe
operation.
5.6.6 Overall ship-wide energy management functionality is to be integrated and
coordinated with the functionality of the local management systems as described in
Vol 3, Pt 1, Ch 6, 3 Definitions for each of the components
(sources, stores, consumers, combinations, distribution system) of the hybrid
electrical power system and is to ensure safe operation of the ship under all normal
and reasonably foreseeable abnormal operating and fault conditions.
5.6.7 Additional energy management functionality for Hybrid Power (+) notation is to
consider, but not be limited to, the following. The level of functionality supplied
is to be consistent with the enhanced performance and dependability required by the
system.
- Control (of the complete system and of each divisible
element):
- Automatic configuration of the power system based on
predicted energy flow;
- Automatic system isolation and reconfiguration such
that, in the event of a single failure in electrical power sources,
stores, distribution system or associated control systems, the impact on
the operational performance of the ship is as agreed with LR and there
is no impact on the ship’s ability to complete its mission;
- System performance optimisation, independent of
primary control functions covering emissions, efficiency, availability,
reliability or operating cost; and
- Control of stores with load smoothing, peak shaving,
dynamic response or other optimisation capability.
- Alarm and monitoring:
- Degradation of power quality;
- Remaining time for continued operation of the power
system at current operating conditions and levels of power consumption.
This may take the form of a real-time performance capability plot;
- System performance covering energy consumption,
emissions, efficiency, availability, reliability or operating cost;
and
- Health and condition of hybrid electrical power
system components including the effects of ageing on electrical energy
storage devices.
- Protection and safety:
- Automatic isolation and reconfiguration of the power
system on detection of abnormal energy flow;
- Consequence analysis determining the remaining time
for continued operation of the power system under stated operating and
load conditions following the most significant single failure. This may
take the form of an onboard off-line simulation derived from, or an
integral element of, the simulation described in Vol 3, Pt 1, Ch 6, 7.6 Energy flows 7.6.3;
and
- Automatic detection of faults detailed in the system
level FMEA with display of mitigating actions.
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