Question: In Eskom and municipal communications, reference is made to “SSEG” systems. What does “SSEG” mean? SSEG stands for a small-scale embedded generation system.
In the context of a residential electricity customer, an SSEG system generally comprises a rooftop solar PV/BES system (see details below), or a standby petrol or diesel generator, or both. The purpose of an SSEG system is to reduce dependence on and the costs of Eskom or municipal electricity, and to ensure continuity of electricity supply in the event of mains power failure caused by load shedding or distribution network outages. Q: In some communications, reference is made to “residential solar PV/BES systems”.
What is a residential solar PV/BES system, and what are the different types of residential solar PV/BES systems? A residential solar PV/BES system generally comprises several roof-top mounted solar photovoltaic (PV) panels, an inverter to convert the DC voltage of the solar PV panels to 50 Hz AC mains voltage, and a DC BES system connected to the inverter. The solar PV/BES system forms part of the customer’s electrical installation and is connected to the customer’s distribution board on the customer’s premises.
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There are various types of residential solar PV/BES systems, including parallel-connected grid-tied hybrid systems, standby systems, and systems for fully off-grid applications. The most common residential solar PV/BES system being installed these days is the grid-tied hybrid system, which may be configured either to be able to import energy from and export excess energy into the distribution network, or to only import energy from the distribution network while blocking exported energy. Q: In some communications, reference is made to an electrical installation “behind the meter” and a solar PV/BES system connected “behind the meter”.
What does this mean, and what does “behind the meter” and “in front of the meter” mean? The main electricity meter for a premises, whether a stand-alone residence, a block of flats or a residential estate/complex, is the property of the electricity distributor – Eskom Distribution or the relevant municipal distributor – and is the point of connection of the customer’s electrical installation to the public distribution network. The boundary between the public distribution network and the customer’s electrical installation is the customer side of the meter.
The public distribution network is referred to as being “in front of the meter”, and the customer’s electrical installation is referred to a being “behind the meter”. Q: In some communications, reference is made to the “Grid Code” or the “Distribution Network Code”, or simply the “Code”. What is this, and is the Code relevant to residential electrical installations and solar PV/BES systems connected behind the meter on a customer’s premises?
The Grid Code or the Distribution Network Code, or simply the Code, is a set of technical rules and requirements approved by the energy regulator, Nersa, governing the performance and operation of Eskom’s transmission grid and the networks of licensed electricity distributors – Eskom Distribution and municipal electricity distributors. The Code also sets rules for connection of customers’ electrical installations to public electricity networks, to ensure system reliability and the safety of network operators in front of the meter. The Code is also to ensure that the connection of particular customer does not create disturbances outside of specified limits that may negatively impact other customers connected to the network – for example electro-magnetic radio frequency interference, over- or under-voltages, dips, sags, spikes, flicker, or excessive distortion of the sinusoidal supply voltage due to current harmonics.
As such, the Distribution Code is relevant to residential electrical installations and solar PV/BES systems connected behind the meter on a customer’s premises. The customer’s electrical installation must be technically compliant with the Code and must not compromise the safety of network operators in front of the meter. Furthermore, electric motors, soft starters, variable speed drives, appliances, and all manner of electrical equipment including solar PV/BES systems, connected behind the meter on a customer’s premises, must not create disturbances outside of specified limits that may negatively impact other customers connected to the network. If they do, the electricity distributor may require the customer to attend to and rectify the matter, or to disconnect the offending equipment.
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