Work Package Configuration details
This page contains information on certain configuration elements that require more explanation or discussion than the regular Work Package Configuration Options page provides.
Span Level Ratings and Improved Network Collapsing
This feature is only available to certain customers. If you are interested in using this feature, please contact Zepben for more information.
The Span Level Ratings feature enables more granular control over network model construction by utilising individual span ratings rather than predefined line type categories. The Improved Network Collapsing allows for faster solve times by collapsing similar network sections based on their electrical characteristics, instead of just exact matches as previously. The rating_threshold and simplify_plsi_threshold can be used with or without Span Level Ratings. It was introduced to manage the additional complexity that span level ratings introduces in terms of node count, and thus reduce solve time back to more manageable levels, but will also benefit models that do not use span level ratings.
Load Modelling Mode
When OpenDSS solves a power flow, it needs to know how each load behaves when voltage rises or falls. Different types of electrical equipment respond differently. A resistive heater draws less power at lower voltage, while some industrial equipment maintains roughly constant power draw across a wide range. This setting lets you choose which behaviour best represents the loads in your network, and affects both the accuracy of results and how reliably the model converges on networks with voltage stress.
Voltage Windows: load_vmin_pu, load_vmax_pu, gen_vmin_pu, gen_vmax_pu
Before describing each mode, it is important to understand these four parameters, as they interact directly with the load modelling mode. They define the per-unit voltage range within which each model's intended behaviour applies. Outside that range, OpenDSS falls back to constant impedance behaviour to keep the solution stable. For example, with load_vmin_pu=0.9, any load bus solving below 0.9 pu will be treated as constant impedance regardless of the mode selected, meaning it will draw less power than specified, without any warning. The generator equivalents (gen_vmin_pu, gen_vmax_pu) apply the same logic to generation assets. Setting these windows wider allows the intended load model to apply across a broader range of network conditions; setting them narrower causes more loads to fall back to constant impedance on stressed networks.
Mode 1 - Constant Power (Default)
The load draws its specified kW and kVAr regardless of voltage, within the window defined by load_vmin_pu and load_vmax_pu. This is generally speaking the standard choice when load data comes from measured consumption such as smart meter interval data, as it uses those values directly. When using this mode it is worth checking solved voltages across the network, any buses outside the voltage window will deliver less load than specified.
Mode 2 - Constant Impedance
Power scales with voltage squared — a 10% voltage drop produces roughly a 19% reduction in power draw. This accurately represents purely resistive loads such as electric water heaters and ovens, and is generally speaking the most numerically stable mode. It is a reliable fallback if Mode 1 is causing convergence difficulties, though it will underestimate consumption in voltage-stressed areas. Note that the load_vmin_pu / load_vmax_pu window has no practical effect in this mode, since constant impedance is already the fallback behaviour.
Mode 3 - 6 These modes are intended for advanced use cases and should only be used in niche use-cases within the HCM. Consult OpenDSS documentation for further information.
Mode 7 - Constant Power, Fixed Impedance Reactive Power
Real power is constant and reactive power varies through a fixed impedance characteristic. This is the mode OpenDSS uses internally for generators.
Which mode should I use?
For most Hosting Capacity studies, Mode 1 is the appropriate choice, as it directly honours your input load data and is consistent with smart meter interval data. If you encounter convergence problems on heavily loaded or low-voltage feeders, Mode 2 is a reliable fallback, with the understanding that results will be slightly conservative in stressed areas. Widening load_vmin_pu and load_vmax_pu is often a better first step than switching modes, as it extends the range over which Mode 1 behaves as intended before falling back to constant impedance. The remaining modes are for specialist studies and are unlikely to be needed for standard hosting capacity analysis.
Network Fixers
Network fixers are a set of pre-processing steps that run before the network is solved.
Whilst this means that the model solved in the power flow model is not a 'true' reflection of the network 'as is' from the ingestors, these fixers are provided as a pragmatic concession to the observed fact that network models and load data are often imperfect, and that getting results for the network with some small tweaks made is better than having a model that doesn't solve at all. They correct common data quality issues in CIM network models that, if left unaddressed, would cause the power flow solver to produce inaccurate results or fail to converge. Each fixer is independently configurable and can be enabled or disabled via the work package configuration.
The fixers operate by reading the load data for each energy consumer across the modelled time period and identifying consumers whose peak load or generation violates a configured threshold. The default thresholds are intentionally generous, as they are designed to catch genuine data errors rather than penalise unusual but valid network configurations, but you can set them how you like.
Single Phase Load Fixer
Config parameters: fix_single_phase_loads, max_single_phase_load
This fixer corrects energy consumers that are recorded as single-phase in the CIM model but have a peak demand too large to be a realistic single-phase connection. The assumption is that a consumer drawing more than max_single_phase_load in watts (default 30,000 W) on a single phase is most likely a three-phase consumer with an incorrect phase assignment in the source data.
What it does:
A consumer is eligible for fixing if all of the following are true:
- It has a peak load across the modelled time period that exceeds
max_single_phase_load - It is single phase
- It is an LV consumer (base voltage at or below 1,000 V)
- It belongs to an LV feeder that is already three-phase at the feeder head (not a single phase transformer)
When a consumer meets these criteria, the fixer reassigns its terminals to three-phase (ABC or ABCN depending on whether a neutral is present). It then traces upstream through the network toward the distribution transformer, progressively spreading three-phase assignments to each conductor and switch it encounters along the way. The trace stops when it reaches a conductor that is already three-phase, or when it reaches the distribution transformer itself.
Overloading Consumer Fixer
Config parameters: fix_overloading_consumers, max_load_tx_ratio, max_gen_tx_ratio
This fixer corrects energy consumers that have a peak demand or generation where they alone are exceeding the capacity of the distribution transformer they are connected to. Consumers in this situation are assumed to be HV industrial or commercial customers that have been incorrectly connected to the LV side of a transformer in the CIM data. The fixer relocates them to the HV terminal of the transformer.
What it does:
For each LV energy consumer, the fixer finds all distribution transformers that supply it (via its LV feeders) and sums their rated capacity (this is typically just one, but can be more than one in rare instances). If the consumer's peak load exceeds max_load_tx_ratio times the total transformer rating, or its peak generation exceeds max_gen_tx_ratio times the total transformer rating, the consumer is moved to the HV terminal of one of those transformers.
Relocation means all terminals of the consumer are disconnected from the LV bus and reconnected to the HV terminal. The consumer's base voltage is updated to match the HV side, and phase assignments are propagated accordingly.
Example: A consumer with a 50 kW peak load connected downstream of a 10 kVA transformer has a load-to-transformer ratio of 5:1. With max_load_tx_ratio = 3.0, this consumer would be detected and moved to the HV terminal of the transformer, treating it as an HV customer.
Undersized Service Line Fixer
Config parameters: fix_undersized_service_lines, max_load_service_line_ratio
This fixer corrects service lines in the network that have current ratings too low for the load they serve, which would cause the solver to report persistent overloads or fail to converge. Unrealistically low ratings are a common data quality issue in CIM models, particularly for service line conductors. The fixer upgrades the affected conductors to a rating and impedance type from a pre-configured catalogue that is appropriate for their phase configuration.
Starting from each energy consumer and tracing upstream, it upgrades any service line conductor whose rating multiplied by max_load_service_line_ratio is less than the consumer's peak load or generation. The trace stops as soon as it reaches a conductor that is sufficiently rated for the load, or when it hits a non service line.
What it does:
For each energy consumer, the fixer calculates its peak load or generation across the modelled time period and uses whichever is larger (largest absolute power value). It then traces upstream from the consumer. For each conductor encountered:
- If the conductor's VA rating multiplied by the
max_load_service_line_ratiois less than the consumer's peak, the conductor is upgraded. - The upgrade replaces the conductor's asset info (current rating and impedance values r, r0, x, x0) with the closest suitable entry from the conductor catalogue that can support the load, matched to the consumer's phase configuration.
Undersized LV Line Fixer
Config parameters: fix_undersized_lv_lines, max_load_lv_line_ratio
It checks the load and traces all the way up to the distribution transformer. It uses max_load_lv_line_ratio as the threshold, which is typically set higher than the service line ratio to avoid upgrading backbone conductors that serve many consumers where a single high-demand consumer would otherwise trigger an upgrade.
What it does:
For each energy consumer, the fixer calculates its peak load or generation across the modelled time period and uses whichever is larger (largest absolute power value). It then traces upstream from the consumer. For each conductor encountered:
- If the conductor's VA rating multiplied by the
max_load_lv_line_ratiois less than the consumer's peak, the conductor is upgraded. - The upgrade replaces the conductor's asset info (current rating and impedance values r, r0, x, x0) with the closest suitable entry from the conductor catalogue that can support the load, matched to the consumer's phase configuration.