A before-and-after APF or SVG comparison is only as useful as its comparison basis. The pre and post records should answer the same question at the same electrical boundary, using known meter settings and comparable operating conditions. Otherwise, a difference in the data may only describe a difference in the plant state.
For broader planning context, start with the руководства по системам качества электроэнергии. This method organizes a controlled comparison; it does not promise a fixed improvement, compliance result, energy saving, or operating outcome.
Прямой ответ
Define the comparison question first, then match or disclose the electrical boundary, meter configuration, time basis, and operating state. Preserve original records from both periods and agree how the project will interpret the comparison before drawing conclusions.
Part 1. Define the comparison question before commissioning
State the question that the comparison is intended to answer. It might concern a defined harmonic-current record, reactive-power behavior at a selected feeder, or a documented operating condition. The wording should identify the boundary and evidence type, not a generic promise to make the plant better.
Assign a review owner and an acceptance method before the post-installation data is collected. This helps the project team decide which records are comparable and which changes need to be disclosed.
Важно: Do not claim a project outcome from a post-installation display alone. The project boundary, operating conditions, and acceptance method must be defined before a comparison can be interpreted (Обзор IEEE 519).
| Comparison purpose | Define before data collection | Доказательства для сохранения |
|---|---|---|
| Гармонический обзор тока | Selected feeder, measurement point, and record type | Pre/post exports and instrument settings |
| Reactive-power review | Electrical objective and operating scenario | Meter fields, load state, and switching state |
| Commissioning verification | Review owner and acceptance method | Installation record and controlled comparison set |
Part 2. Hold the electrical boundary and setup constant
Use the same named electrical location whenever the comparison question permits it. Mark the meter, CT orientation, voltage reference, included circuits, and any parallel path on both one-line diagrams. Keep the instrument configuration, aggregation settings, and time reference with each export.
If a boundary or setup must change, do not hide it. State the change in the report and treat the data as a different scenario unless the project reviewer agrees on a controlled conversion. The APF sizing evidence guide is a separate measurement-led planning resource, not a replacement for a matched comparison.
| Setup item | Keep constant or disclose | Почему это важно |
|---|---|---|
| Electrical location | Meter, CT, voltage reference, and included circuits | Defines the loads represented by the record. |
| Instrument configuration | Settings, interval, and event setup | Avoids comparing differently configured measurements. |
| Time basis | Clock reference and capture duration | Keeps the record windows traceable. |
| Connection state | Bypass, parallel path, and source arrangement | Identifies topology changes that affect comparison. |
Part 3. Match operating conditions before comparing records
Compare like operating states, not calendar dates. Name the shift, production condition, process speed, active drive groups, rectifiers, UPS loads, HVAC loads, capacitor state, and any source or switching change. A quiet maintenance period should not be presented as a direct match for a production peak without clear disclosure.
Use a small set of named scenarios. For each scenario, retain the same measurement boundary and configuration where possible. If a post-installation operating state has no pre-installation equivalent, record it as a separate observation rather than calculating an implied improvement.
| Scenario field | Pre/post record | Avoid assuming |
|---|---|---|
| Production state | Process, speed range, and active lines | That two days automatically have the same load. |
| Major nonlinear loads | Drive, rectifier, or UPS state | That installed nameplate data describes actual operation. |
| Switching condition | Capacitor, bypass, transfer, or maintenance state | That a transient is representative operation. |
| Source configuration | Feeder and supply-side arrangement | That topology stayed unchanged. |
Part 4. Preserve evidence and disclose changes
Keep original data exports, instrument settings, one-line diagrams, operating logs, and installation records together. Label every graph with its boundary, date, time, scenario, and configuration. A concise change log is essential when cables, CTs, sources, load groups, protection settings, or other relevant conditions changed between periods.
Земля SVG commissioning records guide provides installation documentation context. The power-quality baseline report page can help organize pre-installation evidence without becoming a result claim.
| Change to disclose | Record in the comparison package | Review effect |
|---|---|---|
| Measurement change | Meter, CT, voltage reference, setting, or time basis | May make records non-comparable. |
| Load change | Process, production, or coincident-load condition | May explain a different electrical profile. |
| Installation change | Connection point, cable route, cabinet, or bypass state | Defines the post-installation topology. |
| Acceptance change | Metric, responsible reviewer, or decision rule | Prevents an after-the-fact interpretation. |
Part 5. Separate comparison data from a performance promise
Comparison records can support a project review, but they do not create a general performance guarantee. An AHF/APF or SVG discussion still needs a defined objective, connection point, integration scope, protection coordination, installation conditions, and acceptance method.
Земля Контекст продукта: Активный гармонический фильтр AHF page is a starting point when the project evidence and scope are defined. It does not guarantee an improvement percentage, a compliance verdict, or an operating result.
Part 6. Create a project comparison package
Prepare a compact package that allows a reviewer to check whether the pre and post records are comparable. Include raw files as well as the summary chart or table.
| Покупатель должен предоставить | Почему это важно |
|---|---|
| Pre/post one-line diagrams and nominal system details | Identifies the electrical boundary and topology in each period. |
| Meter, CT, voltage-reference, and instrument settings | Makes the acquisition setup traceable. |
| Pre/post exports with time windows | Preserves original evidence behind any chart. |
| Named operating-state logs and load inventories | Tests whether the scenarios are comparable. |
| Installation and switching change log | Discloses differences that affect interpretation. |
| Acceptance method, reviewer, and installation constraints | Defines the project review boundary. |
CNBYG can discuss product-line fit after the comparison package defines the project objective and evidence basis. Use the comparison package to begin that discussion; this method cannot replace a contractual acceptance process or promise an outcome.
Часто задаваемые вопросы
What is a before-and-after APF or SVG comparison?
It is a controlled review of pre and post records collected for the same electrical question. Its value depends on the documented boundary, instrument setup, operating state, and acceptance method.
Must the measurement boundary stay the same?
Yes, whenever the comparison question permits it. If it changes, document the change and treat the records as separate scenarios unless the project reviewer defines a valid comparison method.
How should operating conditions be matched?
Use named scenarios that record process state, load groups, speed, switching condition, and source arrangement. Compare only scenarios that are matched or clearly disclose why they differ.
Does one post-installation reading prove success?
No. A post record needs a defined pre record, matched or disclosed conditions, and an agreed acceptance method before it supports a project conclusion.
What changes should be disclosed?
Disclose measurement setup, electrical boundary, load state, topology, installed equipment, switching condition, time basis, and any acceptance-method change.
What belongs in a comparison package?
Provide pre/post diagrams, system data, measurement settings, original exports, operating logs, change log, installation constraints, and the agreed review method.
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