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© 2019 MOELLER & POELLER ENGINEERING LTD

INTERNATIONAL POWER SYSTEM CONSULTANTS

Power system studies & modelling

MPE has extensive experience of modelling and simulation all power system or power station components for steady state & contingency, quasi-dynamic, short circuit, RMS, EMT, frequency domain / harmonic, protection, or SSR studies. This includes building models suitable for individual power station grid code compliance, G5/4, G5/5, P28, P29, or G74 requirements, or full power system grid integration / expansion planning type studies. Please see the list below for more information on the individual services, then say hello to have a chat with us to see how we can help you with your modelling needs.

load flow & contingency analysis

Our engineers have performed these studies for complete transmission systems, distribution networks, and individual sites, and for a range of purposes. The results often feed into other studies that MPE can undertake such as protection coordination, arc flash and connection studies. The services that MPE offers in this area include:

collecting equipment data in the field
developing a network model
specifying continuous current ratings
assessing existing equipment ratings
specifying transformer impedance & tap ranges
determining generator operating mode
determining generator reactive power requirements
evaluating maximum steady state line capacity
evaluating system reactive compensation requirements
identify required post-fault actions (manual or automatic)
PV and QV curves for assessing steady state voltage stability

short-circuit / fault studies (including ER G74)

Short circuit studies allow assessment of equipment rating (e.g. switchgear, cables, and generation), and provides input into other studies such as protection coordination or earthing design. MPE can perform these studies to any published standard (e.g. IEC 60909 (2016) or ER G74) using a range of software including DIgSILENT PowerFactory, PSS/E, ETAP, or MPE's in house short circuit calculation tool, which can be adjusted to any standard or non-standard fault current calculation method.

Until recently fault current contribution from inverter based equipment (e.g. DFIG and full converter wind generation, PV generation, and HVDC) was neglected in the standards. Given the rise of this type of generation the latest IEC standard now caters for its controllable contribution to fault current. For similar reasons, the UK standard G74 has been recently updated. MPE was the lead technical consultant for this update, on behalf of the Energy Networks Association, to study and propose suitable options to the working group.

RMS (dynamic) studies

Power systems must remain stable for a variety of disturbances, considering a wide range of dynamic responses for different equipment and system configurations. MPE can perform dynamic studies to assess the stability of any network. Our services include:

developing dynamic models for all types of equipment
creating network & controller models in DIgSILENT PowerFactory, PSS®E, PSCAD, ATP, RSCAD, and other software
simulations from 'single machine' to full power system
determining appropriate scenarios to study and performing stability studies
designing mitigation measures to improve or maintain power system stability
performing grid code compliance or grid integration studies for any generator type

EMT (transient) studies & insulation coordination

The results of the EMT studies can be used in insulation coordination procedures to define minimum insulation requirements for equipment, or to design mitigation measures such as surge arresters and sheath voltage limiters. These are designed in accordance with international standards such as IEC 60071 and IEEE C62.82.2.
We also specialise in circuit breaker transient recovery voltage (TRV) simulations to assess circuit breaker dielectric capabilities, and designing the most cost effective mitigation measures where required.
One area of particular expertise for MPE is with transient studies for HVAC connected offshore wind farms with long export cables (up to and in excess of 200 km and 275 kV), and array networks with voltages up to 66 kV.

MPE has world-class experience in conducting electromagnetic transient (EMT) studies to calculate the maximum system overvoltages due to:
fault occurrence/clearing
switching transients
harmonic resonance & transformer energisation
ferroresonance
lightning strike
very fast transients (VFTO) in GIS SF6 substations

harmonic studies

Harmonics in power systems can cause overvoltages, excessive heating of equipment, mal-operation of equipment, and poor power quality for end-users. Our comprehensive study approach considers different system configurations, equipment outages, harmonic voltage gain factors / transfer coefficients, and harmonic impedance loci or full harmonic network models. MPE offers a suite of services including:

requency domain harmonic studies to determine the likely impact of new or modified plant
compliance verification with national and international standards such as IEC 61000, IEEE 519 and UK ER G5/4 and G5/5
measurement for background harmonic assessment
incident investigation
development of harmonic standards
harmonic filter design to mitigate any issues
our speciality is harmonic studies for HVAC connected offshore wind farms (>200 km)

arc-flash assessment

Electrical faults can release significant amounts of energy, endangering personnel. Arc flash studies quantify the hazards posed by these faults, allowing suitable PPE and other mitigations to be put in place.
MPE can conduct complete arc flash studies in accordance with IEEE 1584. Our services in this area include:

collecting equipment data and recording relay settings in the field
developing a network model
calculating incident energy levels and arc flash boundaries
recommending mitigation strategies to reduce arc flash hazards

protection coordination

Our engineers are experienced with protection coordination studies for generators, transmission systems, distribution networks and industrial plants.
MPE offers a wide range of services related to protection systems including:

Developing protection philosophies and standards
Preparing concept and detailed designs for protection systems
Developing logic and setting files for protection relays
Carrying out relay coordination studies
Preparing settings for more complex elements such a distance, differential, restricted earth fault and more
Investigating protection trips and other events
Specifying ratings and accuracy classes for instrument transformers

SSR studies

Sub-synchronous resonance (SSR) studies are typically completed for transmission systems with series-compensated overhead lines near generating plant. The series-connected capacitors can interact with generator mechanical systems, exciting torsional vibration modes and potentially causing severe damage to the turbine-generator shaft system.

If issues are identified, MPE's SSR specialists are able to design mitigation measures to prevent damage to equipment.

modelling of components and networks

MPE can develop customised plant and equipment simulation models, suitable for use with power system analysis software such as DIgSILENT Power Factory, PSCAD, EMTP-ATP, Siemens PSS/E, RSCAD and ETAP.
This service helps developers and manufacturers in fulfilling utility requirements for new generation sites.

We are also experienced in updating and debugging existing network models, as well as migrating models to different software platforms.

grid code compliance studies

We can provide all required grid and distribution code compliance studies for any international requirement (including ENTSO-E requirements) for synchronous or non-synchronous plant. In fact, MPE has developed many of the international requirements found in Grid Codes and Connection Conditions around the world. Therefore we understand the results the utilities are looking for. If non-compliance becomes apparent, then we can propose design modifications or recommend a course of action to resolve the issue, including supporting discussions with the utility / system operator. Examples of the studies we provide include;

reactive capability
reactive power stability and voltage control
PSS tuning & verification
transient stability
fault ride through (FRT),
fast fault current injection,
frequency sensitive mode (frequency response),
LFSM-O & LFSM-U
model verification with compliance tests.

G5/4, P28, P29 studies

Grid owners may request power quality studies prior to allowing connection of new generation or loads to their network. In the UK, these studies are known by the Engineering Recommendation standards G5/4 (harmonics), G5/5 (new harmonic standard) , P28 (rapid voltage change and flicker) and P29 (voltage unbalance).
MPE has substantial expertise in this area — we have completed numerous power quality studies, for sites that are only a few megawatts through to a 2 GW generating plant connected at 400 kV. Our services include:

harmonic studies as per G5/4, G5/5, IEC 61000 and IEEE 519
assessment of flicker and rapid voltage changes in accordance to ER P28, IEC 61000 and IEEE 1789
assessment of voltage unbalance as per ER P29

let's talk

If you have a question about our services, or would like to talk about how we can help with one of your projects then please use the form below, or use the email addresses on our say hello page. Both methods send your query to the same location, where we will find the right person to respond to you as soon as possible: