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KPI Calculation Service – KPI State Calculation

In order to use the KPI calculation functionality of the KPI Calculation Service for a unit, its states have to be known for the time interval of interest. Sometimes various sources, such as sensor readings, control unit data and calendar entries, have to be taken into account to determine the unit's state. The KPI State Calculation can automatically calculate a unit's states from this data.

The following conditions must be fulfilled for this service:

  • Available sensor readings clearly indicate Service states.
  • Available control unit data clearly indicates Forced Outage and Reserve Shutdown states.
  • Available calendar entries define Planned Outage states.
  • When neither sensor nor control unit or calendar provide sufficient information, a default state can be assumed.

Input

This section lists some input parameters, which have to be provided to the KPI State Calculation.

Measurement Data

  • Sensor readings, provided as time series data
  • Calendar entries (planned outage intervals defined by from, to)
  • Control system events (can be NORMAL_STOP, SHUTDOWN)

Initial State

The state which is assumed at the start of the time interval, can be Unknown, SH, RSH, POH or FOH.

Default State

The state to be assumed when there is not enough input data available for state calculation, can be RSH or FOH.

Service Indication Threshold (SIT)

The service indication threshold SIT is required when using sensor data. It defines the minimum value for sensor data, below which the unit is assumed to be stopped.

Shutdown Correlation Threshold (SCT)

The shutdown correlation threshold SCT is required when using control unit data. It is defined as
[Timestamp[i] - SCT, Timestamp[i] + SCT].

Algorithm

Decision process at T=0

Set the state to initial state. If this contradicts a calendar entry, emit an error.

Decision process at T≠0

At each timestamp t≠0, the algorithm evaluates the unit's state using the following decision process:

  1. If a calendar entry is indicates a planned outage at this timestamp, set the state to POH. Otherwise proceed.
  2. If the sensor reading is NULL and all previous sensor readings are NULL, set the state to default state. Otherwise proceed.
  3. If the sensor reading is NULL, use the value of the nearest previous sensor reading ≠0 and proceed.
  4. If the sensor reading is above the Service Indication Threshold (SIT), set the state to SH. Otherwise proceed.
  5. If there is no control system event within the Shutdown Correlation Threshold (SCT), set the state to default state. Otherwise proceed.
  6. If the first control system event within the Shutdown Correlation Threshold (SCT) is SHUTDOWN, set the state to FOH. Otherwise, set it to RSH.

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