What is Distribution Impact Study
- DIS Distribution Impact Study
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Technical parameter for DIS
Distribution Impact Study (DIS) refers to a set of technical studies that are used to assess the possible effects of a proposed expansion, reinforcement, or modification of the distribution system or a user development and to evaluate significant incidents.
That sounds nice, it allows the utility to evaluate the capability of the distribution system to safely and reliably accommodate a proposed interconnection….. but exactly WHAT is done in a DIS?
The scope of the DIS includes the following:
1. Impact of short-circuit infeed on the distribution equipment. Short-circuit infeed is evaluated to determine the impact of the DG installation on the fault level at the connection point. This is very much important since existing equipment connected at that point were sized according to the short-circuit duty prior to the DG installation.
2. Coordination of the protection system. The short-circuit infeed is also assessed to determine its impact on the coordination of the protective devices in the distribution system. The assessment will determine if changes to settings of protection relays, LV-circuit breakers, and trip levels of fuses are necessary.
3. Impact on thermal component ratings and voltage variation. Load flow analysis is conducted to determine the power flows especially during the times when the DG is exporting power to the grid.
4. Impact of user development on power quality. Power quality parameters such as DC current injection, flicker severity, and harmonics are assessed based on energy regulatory standards.
HOW IS IT PERFORMED?
1. Data Gathering. The first step of the DIS is to gather information about the existing customer demand and the RE facility to be installed. Generally, the following data are required:
a. RE system specifying the kVA capacity and voltage rating. The specifications of the solar system, typically of the inverter, solar panels and protective devices.
1. Assessment of RE System Compatibility to the Existing Utility Connection. This is a basic step to ensure that the RE system is compatible with the nominal system voltage at the connection point. There is no easy way of connecting a 120V RE system to a 230V utilization voltage, right?
2. Impact of Short-circuit Infeed on the Distribution Equipment. The next step of the study to assess the impact of the short-circuit contribution of the RE system to the existing fault duty at the distribution system and compare it against the short-circuit rating of existing equipment. This short-circuit information can be found on the RE system type verification test report.
3. Coordination of the protection system. The new fault duty arising from the short-circuit contribution of the RE facility will be used to assess the coordination of protection relays, LV-circuit breakers, and trip levels of fuses are necessary. Time-current coordination study is required in this step.
4. Step 5: Impact on thermal component ratings and voltage variation. Plot the customer load profile and typical generation profile of a RE system with the applied capacity. This is available in many computer software such as ETAP. You can also do an online search of typical generation profiles and scale it to the applied capacity. In this step, we are interested in two extreme cases.
- a. Minimum voltage at the load center, low voltage side; maximum load, and no generation. This is to establish the baseline data at the utility connection point. Thermal component ratings and voltage variations are based only on the customer loads.
- b. Maximum voltage at load center, low voltage side; minimum load (during day-time), and maximum generation. This is the case where the RE facility produces considerably more power than the customer load. In this case, increased thermal loading of transformer, lines or cable, and voltage rise is likely.
6. Impact of user development on power quality.From the RE system type test report, verify the results for DC current injection, flicker severity, and harmonics.
The results of the Distribution Impact Study will determine if the existing distribution system infrastructure can safely and reliably accommodate the proposed connection. In cases where a distribution network upgrade is required, a Distribution Asset Study is conducted in order to define the necessary upgrades.
Solana4U is a primary residential solar installer with 2 branches all over the Visayas Region. Solana4U is happy to answer all your questions.
Contact us by email on hello@solana4u.ph
Keywords: DIS, Distribution Impact Study
