The world of mains protection is changing. G99 mains protection has replaced the long standing G59 connection requirement on 27th April 2019.
G99-1.3 was announced in July 2018 and came into effect from 27th April 2019:
| G99-1.3 | July 2018 | Requirements for the connection of generation equipment in parallel with public distribution networks on or after 27 April 2019 |
As of the 27th April 2019, you will be unable to connect using equipment that is compliant with G59-3.4 only.
You can download a copy of both the EREC (Engineering Recommendation) G59-3.4 and G99-1.3 on this page.
The next update to G99, G99-1.4 is due to be released in June 2019.
The ComAp MainsPro mains protection relay is DNO compliant to the brand new G99-1.3 type-tested standard and is approved on the ENA website. Installing this relay will help to future proof your sites against these upcoming changes in requirements.
There is a difference between type tested and non-type tested equipment. According to the ENA’s G99 document, type tested equipment is defined as:
A product which has been tested to ensure that the design meets the relevant requirements of G99 and that all similar products supplied will be constructed to the same standard and will have the same performance.
Type tested equipment includes inverters (the device that converts Direct Current to nominal frequency Alternating Current).
ComAp’s MainsPro is now classified as fully type-tested. The MainsPro mains protection relay no longer use Vector Shift as a form of Loss of Mains protection as per the latest update to G59-3.4 recommendation.
If a piece of equipment has not been listed on the ENA’s ‘type-tested’ preferred supplier list, it has not been recognised as ‘type-tested’ by the ENA and cannot be used as such. The MainsPro is recognised and approved as type-tested on the ENA website.
G99 compliance differs from G59 in that it applies to a site as a whole, including generators and inverters.
This is why sites that were commissioned before February 2018 do not have to comply with G99. Sites with older equipment will likely not be able to comply, which would mean costly equipment replacements. Sites commissioned before February 2018 must comply with requirements for G59-3.4.
| G99 for Inverters | G99 for Synchronous Power Generating Modules |
| Operating Range | Operating Range |
| PQ – Harmonics | PQ – Harmonics |
| PQ – Voltage Fluctuation and Flicker | PQ – Voltage Fluctuation and Flicker |
| PQ – DC Injection (Power Park Modules only) | Power Factor (PF) |
| Power Factor (PF) | Frequency protection trip and ride through tests |
| Frequency protection trip and ride through tests | Voltage protection trip and ride through tests |
| Voltage protection trip and ride through tests | Protection – Loss of Mains Test, Vector Shift and RoCoF Stability Test |
| Protection – Loss of Mains Test, Vector Shift and RoCoF Stability Test | LFSM-O Test |
| LFSM-O Test | Power Output with Falling Frequency Test |
| Protection – Reconnection Timer | Protection – Reconnection Timer |
| Fault Level Contribution | Fault Level Contribution |
| Self-monitoring Solid State Switch | Logic Interface (input port) |
| Wiring functional tests | |
| Logic Interface (input port) |
| G59-3.4 Calibration & Accuracy Tests | Phase | Setting | Time Delay | Lower Limit |
| Stage 1 Over Voltage | L1 – N |
262.2V |
1.0s | 258.75 |
| L2 – N | ||||
| L3 – N | ||||
| Stage 2 Over Voltage | L1 – N |
273.7V |
0.5s | 270.25 |
| L2 – N | ||||
| L3 – N | ||||
| Stage 1 Under Voltage | L1 – N |
200.1V |
2.5s | 196.65 |
| L2 – N | ||||
| L3 – N | ||||
| Stage 2 Under Voltage |
L1 – N |
184.0V |
0.5s | 180.55 |
| L2 – N | ||||
| L3 – N |
| G99 Calibration & Accuracy Tests | Phase | Setting | Time Delay | Lower Limit |
| Stage 1 Over Voltage | L1 – N |
262.2V |
1.0s | 258.75 |
| L2 – N | ||||
| L3 – N | ||||
| Stage 2 Over Voltage | L1 – N |
273.7V |
0.5s | 270.25 |
| L2 – N | ||||
| L3 – N | ||||
| Under Voltage |
L1 – N |
184.0V |
2.5s | 180.55 |
| L2 – N | ||||
| L3 – N |
For sites connected before February 2018, they do not need to comply with G99 BUT they must comply with G59-3.4. The Accelerated Loss of Mains Change Programme came into effect in April 2019 to encourage sites to ensure full compliance to G59-3.4. You can learn more about the programme, payment allowances and how ComAp can help here.
The power generation landscape has seen a dramatic change over recent years. Instead of relying on a relatively small number of high-capacity power stations, we are turning towards a much larger number of low-capacity generators. Wind farms, photo-voltaic (PV) solar sites and hydro-electric plants are replacing coal and oil power stations. In 2017, renewable sources generated 30% of the UK’s energy.
When talking about generators on power generating sites, we are referring to synchronous generators.
A synchronous generator is known as such because the frequency of the voltage is directly proportional to the RPM.
In the case of asynchronous generating units, the output frequency is regulated by the power system to which the generator is attached.
The output frequency of a synchronous generator can be more easily regulated to remain at a constant value. They are also often more efficient. This is because they can easily be accommodated to load power factor variables.
The rapid expansion of lower-capacity generators can cause the grid to become less stable and this risks damaging both the generator and the grid. Systems that run ‘parallel-to-mains’ must include a relay to decouple the generator from the grid if a problem arises with either.
The European Requirements for Generators (RfG) Code was recently introduced to bring a coherent set of requirements into the power generation market.
There are now 4 types of power generating modules and they are classified by their registered capacity and connection voltage. The types are:
Please note that Type D generators fall under another ENA requirement – G100. This is mainly applicable to Distribution Network Operators (DNOs).
Download the RfG pdf attached to this page to learn more about the requirements for each type.