病院の電気システムにおけるデータ駆動型の電力品質評価
| Facility | University of Lampung Hospital, Indonesia — large university teaching hospital |
| 測定点 | Main Distribution Panel (MDP) — four datasets, high-sampling-rate electrical measurements |
| 適用される規格 | IEEE 1159 (definitions) ・IEC 61000-4-30 (測定方法) ・IEEE 519 (compliance limits) |
| 電圧 & 周波数 | 準拠 — stable, within nominal limits as expected from utility supply |
| Current TDD | NON-COMPLIANT — surpassed IEEE 519 何度も限界を超える |
| Voltage Unbalance Ratio | NON-COMPLIANT — exceeded permitted levels for periods longer than the standard allows |
| 力率 | LAGGING — indicating reactive power losses and reduced distribution efficiency |
| 根本的な原因 | Uncontrolled non-linear loads (SMPS, UPS, VFDは, 映像機器) on internal distribution |
| 重要な発見 | Utility supply was clean — all PQ problems originated inside the hospital’s own distribution system |
01 コンテキストと背景
This case study presents the findings of an extensive, multi-parameter power quality assessment conducted at the University of Lampung Hospital in Indonesia — a large teaching hospital providing both clinical and academic services. The study by Nama, Despa, Tugiyono, and Bangsawan (2025) represents one of the first rigorous, data-driven PQ evaluations at a major Indonesian healthcare facility, filling a gap in regional literature where most prior PQ studies addressed only a single parameter rather than the full spectrum of disturbances.[1]
Modern hospitals are among the most demanding power quality environments in any sector. The load mix is simultaneously highly non-linear — Switch-Mode Power Supplies (SMPS) in computers and monitors, 可変周波数ドライブ (VFDは) in HVAC systems, UPSシステム, diagnostic imaging equipment including CT and MRI scanners — and highly sensitive, with patient monitoring, life-support, and diagnostic instruments that are vulnerable to waveform distortion, 電圧不平衡, and power interruptions.[1]
The most demanding non-linear loads — diagnostic imaging, UPSシステム, electronic ballasts — are the same equipment that generates the harmonic distortion that threatens the sensitive clinical instruments connected to the same distribution system. The hospital is simultaneously its own most significant internal PQ disturbance source and its own most vulnerable victim.
The study is particularly valuable because it applies internationally recognised standards throughout: IEEE 1159 for definitions, IEC 61000-4-30 for measurement methods, とIEEE 519 for compliance assessment. This makes the findings directly comparable to PQ studies in other jurisdictions and relevant to North American and European engineering practice, not only to the Indonesian context.
02 Measurement Methodology
Measurement point and instrumentation
Measurements were taken at the Main Distribution Panel (MDP) — the primary point of supply distribution inside the hospital, downstream of the utility service entrance and upstream of the individual load feeders. Four datasets were acquired using high-sampling-rate electrical measurement equipment. This measurement point captures the aggregate behaviour of all hospital loads as seen from the main supply point, which is the most representative location for assessing the overall internal PQ environment.[1]
測定されたパラメータ
The following power quality parameters were systematically computed from the recorded waveform data:
- Three-phase voltage and current — RMS magnitudes and waveforms for all three phases
- 周波数 — deviation from nominal 50 ヘルツ
- 力率 — ratio of real power to apparent power, with leading/lagging classification
- Voltage Unbalance Ratio (VUR) — ratio of negative-sequence to positive-sequence voltage components per IEC symmetrical components definition
- Total Harmonic Distortion of voltage (THD-V) と 現在 (THD-I)
- 総需要の歪み (TDD) — the IEEE 519 compliance metric for current distortion, referenced to peak demand load current
THD-I is the ratio of harmonic current to the instantaneous fundamental current — it can appear extremely high under light load conditions when the fundamental is small. TDD normalises harmonic current to the system’s peak demand load current (私はザ), giving a stable metric that reflects the actual burden on the network regardless of load level. IEEE 519 specifies TDD limits, not THD-I limits, precisely because TDD is the quantity that determines the voltage distortion seen by all customers on the same supply.[2]
Operational pattern observed
The dataset revealed a strong positive correlation between electrical load and building operational schedule. Peak current loads consistently occurred on weekdays between 06:30 と 17:30 (Monday to Friday), with a marked decrease on weekends. This pattern is important for PQ assessment: 高調波歪み, 電圧不平衡, and power factor all vary with load composition, and a single snapshot measurement would not capture the full range of conditions the distribution system experiences.[1]
03 主な調査結果
Summary of compliance assessment
| Parameter | 標準 / Limit | Observed result | 準拠 |
|---|---|---|---|
| Supply voltage — magnitude | Within nominal limits | Stable — mean within nominal range | 準拠 |
| 周波数 | 50 Hz ± tolerance | Stable — consistent with good utility supply | 準拠 |
| Voltage Unbalance Ratio (VUR) | IN 50160: ≤ 2% のために 95% of week | Exceeded permitted level for periods exceeding the standard’s allowance | NON-COMPLIANT |
| Current TDD | IEEE 519: limit depends on Iサウスカロライナ州/私はザ ratio | Surpassed IEEE 519 何度も限界を超える | NON-COMPLIANT |
| 力率 | Ideally ≥ 0.90 遅れ | Somewhat lagging — indicating reactive power losses | MARGINAL |
| 測定点: Main Distribution Panel (MDP). 基準: IEEE 1159 / IEC 61000-4-30 / IEEE 519. ソース: Nama et al. (2025).[1] | |||
Harmonic distortion — the dominant problem
Current harmonic distortion was the most significant finding. TDD at the MDP surpassed IEEE 519 recommended values by a large margin. This is consistent with the load mix in a modern hospital: SMPS in computers, monitors, and LED lighting; UPSシステム; VFDs in HVAC; and high-power diagnostic imaging equipment — all are non-linear loads that inject harmonic currents into the internal distribution system. The literature cites one reported case where a radiography machine alone produced a current THD exceeding 100%.[1]
第3, ninth, and fifteenth harmonic currents (triplen — odd multiples of 3) are zero-sequence quantities. In a three-phase system they add arithmetically in the neutral conductor rather than cancelling. A hospital with a high density of single-phase SMPS loads — computers, monitors, LED power supplies — can produce neutral currents significantly exceeding the phase conductor current. A neutral conductor sized at 100% of phase ampacity — the legacy default — is undersized for this condition and will overheat silently without tripping any overcurrent device. This is a fire risk as well as a PQ problem.
電圧不平衡
Voltage unbalance exceeded permitted levels for durations beyond what the standard allows. In a hospital, this is particularly consequential because three-phase motor loads — HVAC compressors, ファン, pumps — are sensitive to negative-sequence voltage. A voltage unbalance of 2% can produce rotor current unbalance of 6–10 times the voltage unbalance factor, with corresponding additional heating and accelerated insulation ageing. HVAC の信頼性は患者の快適さと感染制御に直接関係しており、その結果は電気工学の領域をはるかに超えています。.
力率
遅れ力率は、配電システムが局所的な無効電力補償を行わずに、誘導性負荷 (主にモーター負荷と UPS システム) に無効電力を供給していることを示します。. 遅れ力率により、特定の実際の電力需要に対して配電導体と変圧器の皮相電流が増加します。, I²R損失が増加し、配電システムの実効容量が減少する.
04 根本原因の分析
ユーティリティは問題ありませんでした
MDP での電圧と周波数の測定は安定しており、公称制限内であり、適切に規制された公共供給と一致していました。. 観察された PQ 問題は完全に内部起源でした: 病院独自の非線形負荷によって生成される, 病院独自の内部分布インピーダンスを介して循環, 病院自体の機密機器に影響を与える. 電力会社はクリーンな供給を提供した. 病院の内部負荷により劣化した.
これが中心的な発見です, これは、IPQDF ケーススタディで引用されている Fluke フィールド統計と一致しています。 01: 医療施設における PQ 問題の大部分は施設内で発生している. 公共料金メーターの準拠境界は、内部機器の問題の原因を探すのに間違った場所です.
非線形な負荷集中
現代の病院は、他の建物タイプと比較して、単位床面積あたりの非線形荷重密度が非常に高いです。. すべての患者モニター, every infusion pump controller, every computer workstation, every LED luminaire, and every UPS system is a harmonic current source. Unlike industrial facilities where non-linear loads are concentrated in defined production areas, hospital non-linear loads are distributed throughout every ward, every corridor, every administrative office, and every diagnostic room — connected to the same distribution system as the most sensitive clinical equipment.
The strong correlation between PQ problems and operational hours (weekday peak 06:30-17:30) tells the engineer exactly what to look for: the harmonic sources are the equipment that is switched on during clinical hours — diagnostic imaging, patient monitoring, surgical suite loads. The weekend reduction confirms that the baseline harmonic environment from always-on loads (refrigeration, emergency lighting, security systems) is manageable; it is the clinical load that drives the MDP over the IEEE 519 TDD limit.
05 提言
The study authors identified the following mitigation measures as priorities:[1]
- Active harmonic filtering (AHF) — adaptive cancellation of harmonic currents at the MDP or at individual load feeders. AHF adjusts to changing load composition throughout the clinical day, making it well suited to the variable harmonic environment of a hospital
- Load equalization across phases — systematic redistribution of single-phase loads among the three phases to reduce voltage unbalance at the MDP
- 無効電力補償 — local capacitor bank or active reactive compensation to improve power factor and reduce conductor losses
- Neutral conductor sizing review — assessment of triplen harmonic neutral current loading across the distribution system, with upsizing where required
- IoT-based continuous monitoring — real-time PQ monitoring system at the MDP and at key sub-distribution panels, providing early warning of developing harmonic problems before equipment failure occurs
A one-time PQ survey captures a snapshot. A hospital’s PQ environment changes with every shift, every season, and every equipment addition. The correlation between operational schedule and harmonic loading demonstrated in this study argues strongly for permanent monitoring at the MDP — not a periodic survey. The cost of a monitoring system is a fraction of the cost of one diagnostic equipment failure caused by harmonic-induced control malfunction.
06 電力品質の観点
This study is a textbook demonstration of the compliance paradox described in the IPQDF technical overview on power quality. The utility supply was compliant. IEEE 519 at the PCC would have shown nothing wrong. Yet inside the hospital, TDD was exceeding IEEE 519 limits by a large margin, voltage unbalance was out of specification, and the power factor was lagging — all conditions that directly threaten the reliability of clinical equipment and the safety of the distribution system.
From a utility engineering background, the finding is not surprising. Utility engineers know that the PCC is a contractual and metrological boundary, not a protection boundary for the customer’s internal equipment. A clean supply at the meter becomes a distorted supply inside the facility the moment the facility’s own non-linear loads are energised. The degree of distortion depends on the internal impedance of the distribution system — which, unlike the utility network, is not designed to absorb large harmonic currents without voltage distortion.
This study from Indonesia is representative of a finding that repeats across every healthcare facility PQ assessment in the IPQDF case study series: the utility delivers a clean supply; the hospital degrades it internally. The engineering response is not to demand better utility supply quality — it is to conduct an internal EMC audit, measure at equipment terminals rather than at the service entrance, and address the harmonic sources and distribution system inadequacies that the utility standards were never designed to control. EMC audits inside the facility are valuable. The payback is fast — particularly in healthcare, where the cost of a diagnostic instrument failure or a neutral conductor fire can dwarf the cost of the audit and mitigation combined.
参照
- Gigih Forda Nama, Dikpride Despa, Tugiyono, Satria Bangsawan. “Data-Driven Evaluation of Power Quality in Hospital Electrical Systems: Case Study of University of Lampung, Indonesia.” International Journal of Electrical and Electronics Engineering, フライト. 12, しない. 12, PP. 104–116, 2025. DOI: 10.14445/23488379/IJEEE-V12I12P108. Open access under CC BY-NC-ND 4.0.
- IEEE規格 519-2022. 電力システムにおける高調波制御に関する IEEE 規格. IEEE, ニューヨーク, NY, 2022.
- IEEE規格 1159-2019. IEEE が推奨する電力品質監視の実践方法. IEEE, ニューヨーク, NY, 2019.
- IEC 61000-4-30:2015+AMD1:2021. 電磁両立性 (EMC) - 一部 4-30: 電力品質測定方法. IEC, ジュネーブ.
This case study is based on an open-access research article published under CC BY-NC-ND 4.0:
Nama GF, Despa D, Tugiyono, Bangsawan S. “Data-Driven Evaluation of Power Quality in Hospital Electrical Systems: Case Study of University of Lampung, Indonesia.” International Journal of Electrical and Electronics Engineering, 12(12), 104–116, 2025.
DOI: 10.14445/23488379/IJEEE-V12I12P108 ・・ Read the original article →
This case study is presented in summary and commentary form for educational purposes under the open-access terms of the original publication (CC BY-NC-ND 4.0). PQ の視点セクション (セクション 6) represents IPQDF editorial commentary by Denis Ruest, 修士号. (適用済み), P.Eng. (レット。). IPQDF は元の研究の著者であることを主張していません.