उनके स्रोत निर्धारित करने के लिए विद्युत गुणवत्ता घटनाओं के बीच Correlations की स्थापना
| जगह | Industrial neighbourhood — small city, Midwest USA |
| Cause | Bird (crow) flew into medium-voltage utility switchgear — line-to-ground fault |
| Network impact | Voltage sags and momentary interruptions across several miles, affecting 200+ customers |
| निगरानी | Four I-Sense monitors distributed throughout the neighbourhood — GPS time-synchronised |
| Source determination | Time-stamp correlation of 4 monitor records confirmed a single utility-caused grid event |
| Confirmation method | Utility relay operation records matched the GPS timestamp from all four monitors |
| Customer impact | One monitored customer experienced a 13-hour process shutdown |
| Key finding | Multi-point time-synchronised monitoring can attribute PQ events to utility or customer source — resolving the most contentious question in industrial PQ disputes |
01 Context — The Source Attribution Problem
One of the most contentious and practically important questions in industrial power quality engineering is deceptively simple: when a voltage sag or interruption disrupts a customer’s process, who caused it? The answer determines who bears responsibility for the event, who funds any mitigation, and — in regulated utility environments — whether a service quality complaint has merit.
Power quality events may originate from either side of the utility meter:
- Utility-caused (grid events) - पारेषण या वितरण लाइनों पर दोष, स्विचिंग ऑपरेशन, संधारित्र बैंक स्विचिंग, वोल्टेज नियामक संचालन. ये एक ही फीडर या सबस्टेशन से जुड़े सभी ग्राहकों को प्रभावित करते हैं और उपयोगिता की परिचालन जिम्मेदारी हैं
- ग्राहक-प्रेरित (आंतरिक घटनाएँ) - मोटर शुरू होती है, आर्क भट्टी संचालन, संयंत्र के भीतर संधारित्र स्विचिंग, आंतरिक वायरिंग पर खराबी की स्थिति. ये ग्राहक की ज़िम्मेदारी है और उसी वितरण बस से जुड़े पड़ोसी ग्राहकों को भी प्रभावित कर सकती है
- पड़ोसी ग्राहक-जनित घटनाएँ - आसन्न संयंत्र पर एक बड़ा गैर-रैखिक या रुक-रुक कर होने वाला भार (चाप भट्टी, बड़ी मोटर, प्रतिरोध वेल्डर) जो साझा वितरण नेटवर्क के माध्यम से अन्य ग्राहकों तक वोल्टेज गड़बड़ी फैलाता है
उचित निगरानी के बिना - विशेष रूप से, multi-point time-synchronised monitoring that captures the event simultaneously at multiple locations — it is impossible to distinguish these three cases from a single measurement point. A single monitor at the service entrance of a plant records the event but cannot determine whether it originated upstream (utility) or at a neighbouring customer’s premises.
In most jurisdictions, the utility’s obligation to provide power quality within specified limits (voltage magnitude, झिलमिलाहट, harmonics) applies to disturbances that originate from the utility network. If a customer’s process disruption is caused by a neighbouring customer’s operations — a large arc furnace two feeders away, for example — the utility may have limited regulatory obligation to act, even though the affected customer’s experience is identical to a utility-caused event. Source attribution is therefore not just a technical question: it is a prerequisite for assigning responsibility and determining the correct mitigation strategy.
02 The Event — A Bird in the Switchgear
In an industrial neighbourhood in a small Midwestern city, a crow flew into medium-voltage switchgear at a utility substation. The contact between the bird and the energised equipment created a phase-to-ground fault on the distribution system. The fault current caused voltage sags and momentary loss of voltage across a significant portion of the distribution network — affecting customers over several miles and more than 200 ग्राहक खाते.
आई-ग्रिड निगरानी नेटवर्क के हिस्से के रूप में चार आई-सेंस मॉनिटर पूरे पड़ोस में वितरित किए गए थे. प्रत्येक मॉनिटर ने घटना को स्वतंत्र रूप से रिकॉर्ड किया, जीपीएस-सटीक टाइमस्टैम्प के साथ जो रिकॉर्ड किए गए डेटा को समय के साथ सटीक रूप से सहसंबंधित करने की अनुमति देता है.
एक सबस्टेशन पर एक पक्षी के संपर्क के कारण एकल चरण-टू-ग्राउंड दोष से अधिक प्रभावित हुआ 200 कई मील के वितरण नेटवर्क में ग्राहक खाते. यह वोल्टेज सैग्स की नेटवर्क प्रसार विशेषता को दर्शाता है - बिजली रुकावटों के विपरीत, जो आमतौर पर दोषपूर्ण फीडर पर स्थानीयकृत होते हैं, वोल्टेज सैग्स पूरे नेटवर्क में प्रकाश की गति से फैलता है, नेटवर्क प्रतिबाधा टोपोलॉजी के आधार पर आसन्न फीडरों और यहां तक कि आसन्न सबस्टेशनों पर ग्राहकों को प्रभावित करना. The 200+ customers who experienced this event did not share a common feeder — they shared a common substation bus voltage that was depressed by the fault current.
03 Source Attribution — How the Monitoring Proved the Cause
कदम 1 — GPS timestamp correlation
Each I-Sense monitor recorded the voltage event independently, with a GPS-accurate timestamp. When the four records were aligned on a common time axis, all four monitors showed voltage depressions beginning at exactly the same instant — within the GPS synchronisation accuracy of approximately 1 microsecond. This simultaneous onset is the definitive signature of a grid event: an event originating within any individual customer’s premises would reach the other three monitor locations with a measurable propagation delay, not simultaneously.
कदम 2 - तरंगरूप विश्लेषण
सभी चार मॉनिटरों पर तरंगों के विश्लेषण से सिंगल-लाइन-टू-ग्राउंड की विशेषता का पता चला (एसएलजी) दोष - वितरण प्रणालियों पर सबसे आम दोष प्रकार, सभी वितरण दोषों में से लगभग 70-80% के लिए लेखांकन. ध्यान दें कि मॉनिटर #1 लाइन-टू-लाइन वोल्टेज रिकॉर्ड किया गया जबकि अन्य तीन ने लाइन-टू-न्यूट्रल वोल्टेज रिकॉर्ड किया - विभिन्न माप कॉन्फ़िगरेशन ने एक ही घटना से अलग-अलग तरंग आकार उत्पन्न किए, जो समय-सिंक्रनाइज़ेशन संदर्भ के बिना असंगत दिखाई दे सकता है.
कदम 3 - उपयोगिता रिकॉर्ड की पुष्टि
यह परिकल्पना कि सभी चार रिकॉर्डिंग एक एकल उपयोगिता-जनित घटना का प्रतिनिधित्व करती हैं, निश्चित रूप से पुष्टि की गई जब उपयोगिता कंपनी के रिकॉर्ड ने समानांतर फीडर पर एक रिले ऑपरेशन का खुलासा किया, जिसमें सभी चार मॉनिटरों द्वारा दर्ज की गई बिजली की गुणवत्ता की घटनाओं के समान टाइमस्टैम्प था।. रिले ने क्रो-प्रेरित गलती को साफ़ करने के लिए काम किया - एक नियमित सुरक्षात्मक ऑपरेशन - लेकिन इसके टाइमस्टैम्प ने घटना के कारण और समय दोनों की अकाट्य पुष्टि प्रदान की.
यह आयोजन स्पष्ट रूप से उपयोगिता-जनित था. सबस्टेशन स्विचगियर में क्रो-प्रेरित खराबी के कारण प्रभावित वितरण नेटवर्क से जुड़े सभी ग्राहकों के लिए वोल्टेज कम हो गया. किसी भी ग्राहक की कार्रवाई के कारण ईवेंट में योगदान नहीं हुआ. This determination was only possible because of the multi-point GPS-synchronised monitoring network — a single monitor at any one customer’s service entrance would have recorded the sag but could not have distinguished it from a neighbouring customer’s load-switching event.
04 Customer Impact and Mitigation
One of the four monitored customers experienced a 13-hour process shutdown as a result of this event. The shutdown duration is disproportionate to the electrical event duration — the voltage disturbance itself lasted only a few cycles. The 13-hour shutdown reflects the restart time and complexity of the customer’s industrial process, not the duration of the power quality event. This is a common pattern in process industries: a millisecond electrical event causes an hours-long production disruption.
The original study notes that analysis of the waveforms from all four monitor locations shows that commercially available voltage sag mitigation equipment would have protected customer equipment from this event at all four monitored locations. The voltage sag characteristics — depth and duration — were within the operating envelope of dynamic voltage restorers (DVR) and uninterruptible power supply (यूपीएस) systems designed for process protection. A 13-hour production loss from a 3-cycle sag that a $50,000 sag corrector would have prevented entirely illustrates the economics of voltage sag mitigation in process-critical environments.
Implications for monitoring network design
The study draws an important conclusion about monitoring network density. Because grid events — caused by utility network faults — propagate across the network and are experienced simultaneously by all customers in a geographical region, it is not necessary to monitor every customer to assess the power quality environment of a region. A monitoring network covering a small percentage of customers, if properly designed and time-synchronised, provides statistically representative data for the entire region.
This principle has significant implications for utility PQ monitoring program design: sparse, well-placed, time-synchronised monitors can characterise network-wide PQ behaviour far more efficiently than dense, uncoordinated single-point measurements at individual customer service entrances.
05 Power Quality Perspective
This case study is the clearest possible demonstration of why source attribution requires network monitoring — not just customer-side measurement. From a utility engineering perspective, the case study validates a principle that is fundamental to distribution PQ management: grid events are network phenomena, not individual customer phenomena. A crow in a switchgear at one substation produces voltage sags at 200+ customer locations simultaneously. No individual customer measurement, however sophisticated, can identify this as a single grid event rather than 200 separate events.
The GPS synchronisation technology used in the I-Grid system is the key enabler. Without time synchronisation accurate to the microsecond level, the four monitor records could not be reliably correlated — a 60 Hz power system cycle is approximately 16,700 microseconds, and distinguishing simultaneous onset (grid event) from near-simultaneous onset (propagating internal event) requires much better than cycle-level time resolution.
में 30 years of utility power quality work, the source attribution question — “is this our fault or theirs?” — is the most frequently contentious issue between utilities and industrial customers. The customer experiences a process disruption and a production loss. They call the utility. The utility checks its relay records. If no relay operated on the customer’s feeder, the utility concludes the event was internal. The customer disagrees. Without multi-point time-synchronised monitoring, neither side can prove their case definitively. This case study demonstrates that the technology to resolve the question definitively has existed since at least 2003. The gap has been deployment and coordination — not technology. A utility with a well-designed PQ monitoring network can resolve source attribution disputes in minutes. Without one, disputes can last years.
सन्दर्भ
- Divan D, Brumsickle W, Eto J. A New Approach to Power Quality and Electricity Reliability Monitoring — Case Study Illustrations of the Capabilities of the I-Grid™ प्रणाली. अर्नेस्ट ऑरलैंडो लॉरेंस बर्कले राष्ट्रीय प्रयोगशाला, LBNL-52048, अप्रैल 2003.
- आईईईई एसटीडी 1159-2019. IEEE Recommended Practice for Monitoring Electric Power Quality. आईईईई, न्यू यार्क, NY, 2019.
- आईईसी 61000-4-30:2015+एएमडी1:2021. Electromagnetic compatibility — Part 4-30: बिजली की गुणवत्ता माप तरीकों. आईईसी, Geneva.
Divan D, Brumsickle W, Eto J. A New Approach to Power Quality and Electricity Reliability Monitoring — Case Study Illustrations of the Capabilities of the I-Grid™ प्रणाली. Lawrence Berkeley National Laboratory, LBNL-52048, अप्रैल 2003.
This case study is presented in summary and commentary form for educational purposes. Original material is attributed to the authors and Lawrence Berkeley National Laboratory. The PQ Perspective section (अनुभाग 5) and SVG diagram are original IPQDF editorial content by Denis Ruest, M.Sc. (Applied), P.Eng. (ret.). IPQDF does not claim authorship of the original research.