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Carelabs

IEEE 1584 · Engineering

Power System Study & Analysis - Carelabz Russia

Power system study and analysis solves the power flow equations that govern your electrical network, verifying that generators, lines, transformers, and shunt elements perform as intended, withstand expected stress, and are protected against failures. For a Russian facility this brings together load flow analysis, short-circuit and fault analysis, and relay coordination into one connected study. Carelabs performs the full study in ETAP and delivers findings aligned with PUE-7.

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The network has to survive the start

A system study that only solves the steady state misses the condition that actually disrupts plants: the few seconds when a large motor accelerates and pulls the voltage down across the busbar.

What We Deliver

Starting dip at every bus

Voltage is calculated through the acceleration period across the whole network, so the dip is known where sensitive equipment sits rather than only at the motor being started.

WHY IT MATTERS

One motor starts, another line stops

The usual symptom is not a motor that fails to start. It is a contactor releasing on a different circuit, a drive tripping on undervoltage, or a control system resetting, every time one large machine is started.

  • Source impedance taken from the network operator's fault level for the actual connection, since dip depth follows supply strength directly.
  • Load speed-torque and inertia characteristics taken from the driven machine rather than assumed, because they govern how long the start lasts.
  • Dip assessed against the tolerance of sensitive equipment on the same busbar, not against a generic limit at the point of supply.
  • Standby generation modelled separately where present, as generator impedance produces a substantially deeper dip than the utility.
  • Repeated starting duty assessed where the process requires it, since thermal limits rather than electrical ones govern permissible restart frequency.
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DELIVERABLES

What you receive

Issued against PUE-7 and GOST R 50571, with the load characteristics and supply basis stated explicitly.

  1. 1Steady-state bus voltages and branch loading as the pre-start condition
  2. 2Voltage dip profile at every bus through the acceleration period
  3. 3Acceleration time with torque margin shown against the driven load
  4. 4Comparison of starting methods where the dip is unacceptable
  5. 5Protection and undervoltage settings that permit the start while still protecting the motor
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How the study runs

01

Establish the steady state

Load flow is solved first, because the voltage present before a start determines how deep the resulting dip goes.

02

Collect motor and load data

Nameplate values, starting characteristics and the driven machine's torque and inertia data are gathered, since the load governs the outcome.

03

Model the network and sources

Source impedance is derived from the operator's fault level, and any standby generation is modelled as its own case.

04

Simulate the start

Acceleration is simulated with voltage, current, torque and speed tracked throughout, on each supply the site can run on.

05

Test the alternatives

Where the dip is unacceptable, starting methods are compared on the same model so the recommendation rests on simulation rather than preference.

06

Report and settings

Findings are issued with the recommended arrangement and protection settings that accommodate the start without compromising protection.

Frequently asked questions

It is set by the most sensitive load on the affected busbar rather than by a single figure. Contactors typically release somewhere below 70 to 80 percent of rated voltage and electronic equipment varies widely. This is why dip is reported at every bus rather than only at the motor being started.
Because it shares the model and depends on the steady-state result. The voltage present before a start determines how deep the dip goes, so a starting study run on an assumed pre-start voltage understates it. Combining them costs little extra once the network has been captured and verified.
Not always. It reduces starting current and therefore the dip, but it reduces available torque at the same time. On a high-inertia or high-breakaway load that can produce a start that is too slow or does not complete. Where torque is the binding constraint, a variable speed drive or different motor selection is needed.
Substantially. Generator impedance is much higher than the utility supply, so the same motor produces a considerably deeper dip, and on a generator the frequency falls as well as the voltage. Sites frequently discover this during an outage rather than in planning, which is why the generator case is modelled separately.

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