Chapter 5: PCS (energy storage converter) operation and maintenance standards
This chapter stipulates the standardized operations for daily inspection and preventive maintenance of the hybrid inverter (PCS) by CoreTect authorized engineers. ⚠️ Note: This chapter only covers the O&M (operation and maintenance) level. Engineers are strictly prohibited from performing motherboard-level welding repairs on site.
5.1 PCS Safety Isolation and Electrical Test Specification (LOTO)
Before performing any operation to open the inverter wiring compartment cover, the following discharge red lines must be strictly observed:
1. Disconnect AC and DC: Disconnect the AC grid circuit breaker, load circuit breaker, PV isolation switch and battery DC main gate in sequence.
2. Force the static capacitor to discharge: After powering off, force the device to wait for ≥ 5 minutes (models above 100kW need to wait 15 minutes) to allow the internal DC-Link large-capacity electrolytic capacitor to completely discharge.
3. High-voltage electrical test: Wear insulating gloves and use a multimeter at the DC 1000V range to measure BAT+ and BAT-. Only after confirming that the internal residual voltage is < 36V DC can you start touching.
5.2 PCS electrical connection and torque maintenance
Since the inverter operates under high current and thermal expansion and contraction conditions for a long time, the AC and DC terminals can easily become loose and cause arc fire.
1. Thermal imaging inspection (performed with power on): When running at full load every quarter, use an infrared thermal imaging camera to scan the GRID/LOAD AC output terminals and BAT/PV DC terminals. If the terminal temperature is > 65°C, or the temperature difference between phases is > 5°C, it is marked as abnormal.
2. Torque retightening (executed when power is off): Use an insulated torque wrench to retighten the detected abnormal heating points (reference standards: M6 bolts 5N·m, M8 bolts 12N·m, M12 bolts 45N·m), and redraw the red/blue anti-loosening lines.
5.3 PCS heat dissipation and dust-proof maintenance
The life of the inverter is determined by the heat dissipation of the IGBTs. In the high dust environment of the Philippines, strict implementation is required:
1. External dust filter: During monthly inspection, remove the dust filter from the bottom/side air inlet of the inverter, use a high-pressure air gun (pressure < 0.3MPa) or clean water to rinse and dry it thoroughly before reinstalling it.
2. Cooling fan test: Force the fan to run at 100% through the on-screen diagnostic menu. If there is abnormal bearing noise or speed alarm, it must be recorded and the fan module must be replaced as a whole during the next inspection.
Chapter 6: Communication and Cloud Platform Operation and Maintenance Standards
Communication links are the lifeblood of CoreTect's SaaS services and remote risk control, and must ensure an online rate of 99.9%.
6.1 Physical Link Layer Check (Physical Layer)
- Anti-interference of communication cables: Check whether the RS485 and CAN communication lines use shielded twisted pairs (Shielded Twisted
Pair). The shield must be connected to ground at one end at the inverter end. It is strictly prohibited to bundle communication lines and AC and DC thick cables in parallel in the same cable trough. They must be kept 15cm apart.
以上间距。
- Terminal matching resistor: If the bus distance exceeds 50 meters or there is serious garbled packet loss on site, check whether the A/B pins of the device at the end of the bus have been connected in parallel with a 120Ω terminal resistor.
6.2 Edge Intelligent Gateway (4G DTU/ESP32) Operation and Maintenance
- Signal dead zone test: Check the RSSI value of the gateway background. Standard requirements RSSI >
-85dBm. If the signal is lower than this value, it is strictly forbidden to lock the antenna in the metal cabinet. You must use an extension cord to move the suction cup antenna to an unobstructed place outdoors.
- Watchdog and reconnection test (Watchdog Test): Unplug the 4G gateway antenna on site to simulate a network disconnection, and observe whether the gateway can be disconnected within 300
Trigger the hardware watchdog within seconds, automatically power off, restart and reconnect.
CoreTect ThingsBoard cloud platform.
Chapter 7: Failure Response and RCA Investigation
7.1 Service Level Agreement (SLA) Response Matrix
Based on the SaaS level of customer subscription, CoreTect Operation and Maintenance Center strictly implements the following response time:
- 🚨 Level P1 (major failure): PCS down/fire alarm/battery communication offline.
- Response mechanism: The cloud intervenes and issues a safe power-off command within 30 minutes; Metro Manila area engineers arrive at the scene with spare parts within 4 hours.
- ⚠️Level P2 (general failure): cell voltage difference > 100mV / battery environment high temperature warning.
- Response mechanism: The cloud will respond within 4 hours and try to issue remote balancing instructions; if it does not recover, on-site investigation will be conducted within 24 hours.
- ℹ️ Level P3 (minor abnormality): Weak 4G signal causes occasional data delays.
- Response mechanism: Register within 24 hours and resolve the issue during the next routine inspection.
7.2 Major accident RCA (root cause analysis) and liability investigation
When P1-level equipment blows up or a customer makes a claim, engineers must issue an 8D standard RCA report within 48 hours to clarify the responsibility (line of defense):
1. Evidence collection of illegal loads: Check the distribution box on site. If a customer is found to have privately connected a large inductive load such as a deep well water pump, take photos and collect evidence, and it will be determined as [reverse electromotive force breakdown IGBT], which is a human violation by the customer and the warranty will be refused.
2. Harsh environment evidence collection: If you find water leaking from the roof and dripping into the cabinet, or the tamper-resistant warranty seal (Warranty Seal) is torn, immediately shut down the machine and take photos.
3. Black box log extraction: Use a computer to connect to the BMS/PCS, export the underlying logs 5 minutes before the crash, and analyze whether there is an ultra-high voltage surge in the power grid (Grid
Surge). If the power grid is struck by lightning, it is a force majeure event.
Chapter 8: Philippine Field Operation and Maintenance Standards (PH Localized Standards)
Special operation and maintenance specifications are formulated based on the tropical island climate and underdeveloped power grid environment of the Philippines.
8.1 Extreme moisture resistance and salt spray resistance (Anti-Corrosion Protocol)
- Contact sealing: The Philippines has high humidity and salt, which can easily cause green patina or electrochemical corrosion on electrical terminals. During inspection, the oxide layer must be cleaned with electronic cleaner, industrial conductive paste should be applied after tightening, and polyurethane conformal paint should be sprayed
(Conformal Coating) Completely isolates moisture.
- Anti-condensation management: During rainy season inspections, it is necessary to check whether the anti-condensation heating plate at the bottom of the cabinet is working properly to prevent water vapor from condensing and causing high-voltage discharge.
8.2 防虫鼠害灾难排查 (Pest Control)
- Geckos (Tuko), rats, and red ants are the number one killers of motherboard short circuits in the Philippines.
- Mandatory action: Every time you open a cabinet, you must clean up the debris at the bottom. Firestop Putty must be used in the cable entry and exit holes inside and outside the cabinet.
Seal tightly; industrial insect repellent/rodent repellent tablets must be regularly placed in the corners of the electrical cabin.
8.3 Typhoon and Flooding Emergency Plan (Typhoon Emergency SOP)
- 48 hours before typhoon (Pre-Typhoon): The cloud issues a mandatory charging command to increase the battery SOC lower limit to 90% in preparation for war.
- Flood rescue (Flood): If the water level warning submerges 10cm from the bottom of the cabinet, the DC main gate will be forcibly cut off remotely/on-site and the power supply of the 4G gateway will be unplugged.
- Red line for water receding and recovery: Customers are strictly prohibited from closing the gate on their own! An engineer must come to clean and dry the device, and use a 1000V megger to measure the AC and DC insulation resistance > 2MΩ before powering on again.
Chapter 9: Customer Service and Asset Management
This chapter establishes CoreTect’s commercial implementation mechanism for transforming “low-frequency maintenance” into “high-frequency value-added services”.
9.1 SOH life tracking and asset health score (Health Score)
- The cloud system integrates underlying data such as SOC, SOH, maximum pressure difference, and historical overtemperature times, and uses algorithms to automatically generate a 100-point "health score".
- Monthly Health Report: The system automatically generates a PDF report and sends it to the customer on the first day of each month.
- Commercial conversion: For sub-health assets with a score lower than 80 points, customer service proactively sends early warnings and attaches a "CoreTect Deep Balance and Life Extension Maintenance Quotation" to achieve proactive marketing.
9.2 White-Label system (White-Label) and agent management
- For large installers (Installer), CoreTect provides cloud ThingsBoard tenant-level permissions (Tenant Admin).
- Brand Enabling: Replace the proprietary logo and domain name in the system interface to enable the agency business.
- Ultimate risk control (Kill-Switch): CoreTect Asia Pacific headquarters retains the final control of the underlying gateway. If the agent maliciously defaults on SaaS
For a subscription fee, the headquarters has the right to cut off communications and even issue power-off instructions with one click on the cloud.
9.3 Spare parts warehousing and sluggish material flow (Spare Parts Management)
- Safety stock bottom line (Min-Max Inventory): Marikina laboratory needs to maintain core consumables (such as 4G
Gateway, DC circuit breaker, fuse tube, spare battery core) are above the safety stock water level.
- One-in, one-out principle: Engineers apply for new motherboards/gateways and go to the site for repairs. When they return, they must return the burned old parts and enter them into the black box system for write-off, to prevent spare parts from being lost or resold without permission.
Chapter 10: Rooftop Photovoltaic (PV) Troubleshooting and Practical Demining Guide
Note: According to CoreTect big data statistics, 70% of inverters in the Philippines report errors, and the root cause is the rooftop photovoltaic array (periphery). This chapter combines front-line practical experience to specifically deal with high-frequency deadlocks on the PV side.
10.1 "Voltage but no current (virtual electricity)" ghost troubleshooting method
Phenomenon description: The inverter does not generate electricity. Use a multimeter to measure the open circuit voltage at the PV port of about 400V, but after closing the DC switch, the input current at the inverter end is always 0A.
Actual root cause (RCA): This is a typical "virtual connection". It often occurs when the MC4 connector is not pressed tightly, the wire core is oxidized and broken, leaving only a single wire connected, or the bypass diode in the photovoltaic module junction box has a thermal breakdown and open circuit.
Troubleshooting standards: It is strictly prohibited to rely solely on a multimeter to measure the no-load voltage qualitatively! The MC4 connectors of the rooftop strings must be disconnected one by one and scanned with an infrared thermal imaging camera at the moment when the load is attempted. The connectors with abnormally high temperatures are virtual contacts. Simply cut away and redo the MC4 connector using professional crimping pliers.
10.2 “DC Arc & Isolation” fatal precautions
Phenomenon description: The inverter reports that the PV insulation resistance is too low (Isolation Fault). Forcibly closing the inverter may hear the hissing discharge sound from the roof.
Actual Root Cause (RCA): High incidence during the rainy season in the Philippines. Rats/pests chew the wire sheath, or the cable is damaged by long-term friction at the sharp edge of the color steel tile. Once high-voltage DC discharges to the ground, it is easy to pull out an arc with a high temperature of several thousand degrees and burn the roof.
排查标准：
Must use 1000V megohmmeter to measure. It is strictly prohibited to use an ordinary multimeter (the voltage of the multimeter is only 9V and cannot penetrate the water film to find leaks).
Carry out the "dichotomy" investigation: disconnect the string from the middle, conduct segmental shake measurements, and quickly approach the leaky photovoltaic panel or cable segment.
After repair, all DC cables passing through the iron roof must be compulsorily installed with flame-retardant corrugated conduits and silicone sealants.
10.3 “DC Voltage Reverse Current” Fire Prevention Verification
Phenomenon description: When multiple photovoltaic groups are connected in series and parallel to the same MPPT of the inverter, the total power generation is far lower than expected, and the surface temperature of a certain group of photovoltaic panels is abnormally high.
Actual root cause (RCA): The voltage difference occurs due to the different shadow occlusion conditions of the two strings or the inconsistent number of series blocks. The current of the high-voltage string does not enter the inverter, but flows back to the low-voltage string, serving as a load for continuous heating.
Troubleshooting criteria: Disconnect the parallel connection point and measure the open circuit voltage of each string. If the voltage difference is > 10V, direct parallel connection is strictly prohibited! It is mandatory to install a 15A/1000V photovoltaic anti-reverse charging diode (Blocking Diode) in the combiner box or re-plan the string wiring.
10.4 DC/AC Ratio Imbalance Assessment
Phenomenon description: The inverter cooling fan spins wildly, the chassis temperature is too high, and the over-temperature load reduction protection is often triggered at noon.
Actual verification: retrieve the rated input power from the inverter nameplate and check the total power of the actually installed photovoltaic modules. If the capacity ratio (total photovoltaic power ÷ inverter power) > 1.5 (depending on the specific model), it is determined to be excessive over-provisioning.
Solution: Issue a capacity expansion proposal to the customer. It is recommended to install an energy storage battery module to absorb excess peak energy, or to increase the parallel inverter shunt, otherwise the inverter extended warranty service will be refused.
Chapter 10: Investigation and rescue procedures for fatal hidden dangers on the roof photovoltaic side (PV)
This chapter is extracted from the practical experience of front-line senior operation and maintenance. In the Philippine market, due to extremely irregular construction by local installers, 90% of fatal failures reported by inverters are caused by peripheral cables on the roof. This chapter is CoreTect’s core guide to charging high Troubleshooting Work Fees.
10.1 Fake Voltage & Burned MC4
(Corresponding information: There is voltage but no current, and colleagues who can see the fault at a glance (scorched connectors))
• Phenomenon description: The inverter does not generate electricity. The multimeter measured a voltage of about 400V at the PV end, but when it was turned on, the current was always 0A.
• Old Cannon Root Cause (RCA): This is the classic “virtual electricity” trap for newbies. The root cause is usually that the internal metal pins of the MC4 plastic connector on the roof are not crimped tightly (virtually connected). When there is no load, the energy reaches the voltage. Once the inverter draws a large current, a high temperature of several hundred degrees will be generated at the joint instantly, directly burning the internal copper core or melting the plastic shell (such as the burnt joint shown by the veteran).
• 抢救 SOP：
1. It is strictly prohibited to only measure voltage! A thermal imaging camera must be carried on the roof.
2. Scan all MC4 connectors while the inverter attempts to pull load. The red and hot connector is the culprit!
3. Cut off the burned connector and use professional photovoltaic crimping pliers to re-press the new MC4.
4. Commercial charges: Replacement of one joint costs 10 pesos, and a “roof depth demining fee” starts at 3,000 pesos!
10.2 DC Arc & Isolation Fault
(Corresponding information: insulation resistance alarm shutdown, DC arc fire)
• Phenomenon description: After the rainy season or strong winds, the inverter frequently crashes and reports Isolation Fault (low insulation resistance). There is even a burning smell on the roof and fire in the wires.
• Old root causes (RCA): Philippine rats chew the wire sheath, or photovoltaic cables are rubbed and broken at the sharp corners of the color steel tiles for a long time. Once the 600V DC high voltage comes into contact with the water film or metal roof, it will pull out an extremely terrifying "DC Arc"** and instantly ignite the surrounding weeds or houses!
• 抢救 SOP：
1. The red line of death: Once arcing occurs, it is strictly prohibited to splash water directly! The DC switch at the bottom of the inverter must be pulled down immediately!
2. Megger tracking: After the inverter is powered off, unplug the PV wire. Use a 1000V megger to measure the impedance of the positive and negative poles to ground. If it is < 1MΩ, go to the roof immediately, cut the cables in sections, and conduct shake measurements until you find the leakage point.
3. Commercial charges: Issue a "Fire Hazard Investigation Report" to persuade the customer to carry out the "Full Roof Cable Flame-Retardant Pipe Reconstruction Project", the quotation starts at 20,000 pesos! **
10.3 Over-temperature load reduction and unbalanced capacity ratio of the inverter (Over-Temp & Clipping)
(Corresponding information: Inverter over-temperature alarm, power generation continues to decrease, capacity ratio imbalance)
• Phenomenon description: When the sun is strongest at noon, the inverter alarms and the fan spins wildly, and the power generation not only does not increase but decreases.
• 老炮根因 (RCA)：
1. The installer’s greed: In order to make more money, the contractor installed 18kW photovoltaic panels (capacity ratio > 1.8) for the 10kW inverter. All the excess energy is stored in the inverter and turns into a high temperature of several hundred degrees!
2. Environmental strangulation: The computer room is airtight, and all the inverter inhales is hot air, which triggers the motherboard's "Thermal Derating" self-protection mechanism.
• 抢救 SOP：
1. Check the total power of the components actually installed on site and compare it with the inverter nameplate.
2. If the over-provisioning is serious, the excess strings must be removed, or the customer may be advised to purchase an additional CoreTect inverter for shunting.
3. It is mandatory to install a high-power industrial exhaust fan in the computer room and aim it at the inverter’s cooling fins to draw strong air.
10.4 Four “Yield Killers” with Low Power Generation
(Corresponding information: Why your photovoltaic power generation is lower than that of your neighbors and why the power generation does not meet the standard)
When a customer complains that the system does not save power, do not suspect that the machine is broken. Take the customer directly to the roof to verify these 4 points:
1. Severe shading: Even if only 10% of a board is covered by a tall tree growing next to it or a neighbor’s new second floor, the power generation of the entire string of boards will plummet by 50% due to the “barrel effect”! (Countermeasure: Prune branches, or install Optimizer).
2. Dust-heavy areas: As a veteran said, "3 megawatts a day can't be washed out." The Philippines has a long dry season, and the bird droppings and thick ash layer on the boards will seriously block sunlight. (Business conversion: Launch of "quarterly professional photovoltaic panel cleaning service", annual fee).
3. Micro-cracks: The contractor stepped on the photovoltaic panels during construction, causing the internal crystalline silicon to break. Invisible to the naked eye, the "heat black spots" must be scanned out with a thermal imaging camera or EL tester.
4. Grounding Issue: Such as veteran video (ground resistance detection). If the ground stake is not installed or the resistance value is > 4Ω, it is not only vulnerable to lightning strikes, but also interferes with the high-frequency leakage current detection of the inverter, causing inexplicable shutdowns.