State Grid Corporation of China Verified SupplierOne-Stop Supply of Conventional & Solar Power Equipment
QDTB® TransformerPowering the Future Since 2001
⚠️ Reference estimates (FOB Qingdao, EXW) for preliminary design only — not a final quote. Confirm with a qualified engineer per IEC 60364 / 60909 / 62271.
Power Distribution
Solar Power

⚙️ Distribution System Calculator System-level

📖 About this calculator

Enter your total connected load and get a complete power distribution system design — transformer, HV & LV switchgear, power-factor correction, cables, busbar and grounding — with a full bill of materials and FOB Qingdao price.

🧭 How to use

  1. Enter total connected load (kW) and average power factor.
  2. Pick transformer type, voltages and a scenario preset.
  3. The full BOM — models, quantities and prices — appears instantly on the right.
⚠️ Reference design & price estimates (FOB Qingdao, EXW) for preliminary planning only — not a final quote. Confirm ratings with a qualified engineer per IEC 60364 / 62271 / 60909.

⚙️ Project & Loads

Your grid's high-voltage level
Your low-voltage distribution level
Enter your real total connected load — this drives the whole system design & BOM.
Your loads' real average PF (0.5–1)
🔌 Circuits (auto-split)

📊 Complete System Design

Fill in your project & loads on the left — the full system design and bill of materials appear here instantly.

🔌 Transformer Selection Calculator

📖 About this calculator

Size and price a transformer from your load — oil-immersed, dry-type, amorphous-alloy or box-type substation — with live copper-price linkage.

🧭 How to use

  1. Enter connected load (kW).
  2. Pick equipment type and ratings.
  3. Get the standard kVA, model and reference price.
⚠️ Prices are reference estimates (FOB Qingdao, EXW), not final quotes. Sizing is preliminary — verify against your project and local standards.

⚙️ Your Load & Specs

📊 Result

Fill in your load on the left — the result appears here instantly.

⚡ Short-Circuit Calculator

📖 About this calculator

Calculate low-voltage short-circuit current and pick a matching breaker by rated current and breaking capacity (IEC / NEC).

🧭 How to use

  1. Enter transformer kVA and impedance.
  2. Pick the standard (IEC / NEC).
  3. Get Isc and the recommended breaker model.
⚠️ Reference values for preliminary design. Final protection settings must be verified by a qualified engineer per IEC 60909 / NEC 110.

⚙️ Transformer & System

📊 Result

🔋 HV Short-Circuit Calculator

📖 About this calculator

Calculate high-voltage short-circuit current from the upstream short-circuit capacity and verify switchgear rating (KYN28A / KYN61).

🧭 How to use

  1. Enter short-circuit capacity and voltage.
  2. Get the short-circuit current.
  3. See the recommended switchgear model.
⚠️ Reference values for preliminary switchgear selection. Final short-circuit rating must be verified per IEC 62271-100 / IEEE C37 by a qualified engineer.

⚙️ System

📊 Result

🔗 Voltage Drop Calculator

📖 About this calculator

Size a cable by ampacity and voltage drop — single- or three-phase, copper or aluminum.

🧭 How to use

  1. Enter current, length and material.
  2. Pick phase and maximum voltage drop.
  3. Get the recommended cable cross-section.
⚠️ Based on IEC 60364-5-52 reference ampacities. Final cable selection must consider installation method, temperature and local code.

⚙️ Circuit

📊 Result

🌀 Power Factor Calculator

📖 About this calculator

Calculate the capacitor kVAR needed to correct power factor from PF1 to PF2.

🧭 How to use

  1. Enter load kW and both power factors.
  2. Get the required compensation kVAR.
⚠️ Reference estimate. Final capacitor bank selection must consider harmonics, switching and voltage.

⚙️ Load

📊 Result

🌍 Grounding Calculator

📖 About this calculator

Calculate grounding resistance for vertical earth rods and the number of rods to meet a target resistance.

🧭 How to use

  1. Enter soil resistivity, rod length/diameter and target resistance.
  2. Get resistance per rod and the required rod count.
⚠️ Simplified rod-electrode model. Final grounding design must be measured on-site and verified per IEEE 80 / IEC 62305.

⚙️ Electrode

📊 Result

🧲 Reactor Calculator

📖 About this calculator

Size a series or shunt reactor from capacitor kVAR × impedance ratio, with reference FOB price (CKSG / BKSC).

🧭 How to use

  1. Enter capacitor kVAR and impedance %.
  2. Pick the connection type.
  3. Get reactor kVAR and reference price.
⚠️ Reference estimate for preliminary sizing. Final reactor rating must be verified per IEC 60076-6 / GB by a qualified engineer.

⚙️ Capacitor Bank

📊 Result

📦 Branch Box Calculator

📖 About this calculator

Get a reference FOB price for a cable branch box (DFW series) by voltage, rated current and quantity.

🧭 How to use

  1. Pick voltage, rated current and quantity.
  2. Get the DFW model and reference price.
⚠️ Reference price based on a stainless-steel, 1-in / 4-out branch box. Final quote depends on way count, enclosure and accessories.

⚙️ Specs

📊 Result

☀️ Solar Power System Configurator System-level

📖 About this calculator

Enter your application & load and get a complete solar power system — PV array, inverter, battery, mounting, cables and grid connection — with a full bill of materials, single-line diagram and FOB Qingdao price.

🧭 How to use

  1. Pick an application scenario (residential grid-tie / off-grid, C&I grid-tie / storage).
  2. Enter total load (kW) and, for off-grid / storage, daily consumption (kWh).
  3. The full BOM and single-line diagram appear instantly on the right.
⚠️ Reference design & price estimates (FOB Qingdao, EXW) for preliminary planning only — not a final quote. Confirm with a qualified engineer per IEC 60364 / 62548 / 62109.

☀️ Application & Load

Enter your real total load (kW)

📊 Complete System Design

Fill in your application & load on the left — the full BOM and single-line diagram appear here instantly.

🔌 PV String Designer

📖 About this calculator

Design a PV string against inverter limits — temperature-corrected Voc / Vmp, MPPT voltage window, current per MPPT and the DC/AC ratio. Prevents over-voltage in cold weather and under-voltage in hot weather.

🧭 How to use

  1. Pick your module power and inverter rating.
  2. Set the site’s min / max ambient temperature.
  3. Optionally enter a target DC capacity to get string count and DC/AC ratio.
⚠️ Design guide per IEC 62548 — verify with a qualified engineer before installation.

🔌 Module & Inverter

📊 String Design

Pick a module and inverter — the recommended string size appears here instantly.

🔋 Battery Sizing Calculator

📖 About this calculator

Size an energy-storage battery for backup or peak-shaving — required capacity from load & autonomy, series/parallel configuration, DoD-driven cycle life, C-rate check and matching PCS.

🧭 How to use

  1. Enter the load (kW) and required backup duration (h).
  2. Pick the system voltage (low-voltage 51.2 V or a high-voltage cluster).
  3. Choose the depth of discharge — capacity, cycle life and PCS update instantly.
⚠️ Reference sizing & price estimates (FOB Qingdao, EXW) for planning only.

🔋 Load & Autonomy

📊 Battery Design

Enter the load and backup duration — capacity, configuration and BOM appear here instantly.

🔗 PV Cable Voltage-Drop

📖 About this calculator

Check the DC-side voltage drop and line loss of a PV string, verify cable ampacity (1.25 x Isc) and pick the minimum section to stay under the 2% drop guideline.

🧭 How to use

  1. Enter string current (Imp) and one-way cable distance.
  2. Pick the cable section and string voltage.
  3. The drop %, line loss and recommended section appear instantly.
⚠️ DC drop guideline < 2% per IEC 60364 / 62548.

🔗 String & Cable

📊 Voltage-Drop Result

Enter the string current and distance — voltage drop and cable sizing appear here instantly.

💰 Solar Yield & Payback

📖 About this calculator

Estimate annual energy yield, levelized cost of energy (LCOE), simple payback and 25-year net profit — with module degradation, tariff and your system cost.

🧭 How to use

  1. Enter installed capacity, peak sun hours and performance ratio.
  2. Enter your electricity tariff and system cost (or leave cost blank to estimate).
  3. LCOE, payback and net profit appear instantly.
⚠️ Estimates for planning only — actual yield depends on site irradiation, orientation and losses.

💰 Energy & Finance

📊 Yield & Payback

Enter capacity and sun hours — yield, LCOE and payback appear here instantly.

📐 Mounting Tilt & Spacing

📖 About this calculator

Find the optimal tilt angle for a location and the row spacing needed to avoid winter-solstice shading — using the site latitude and module dimensions.

🧭 How to use

  1. Pick the site latitude (or enter it).
  2. Leave tilt blank to auto-optimize, or set it manually.
  3. The optimal angle and row pitch appear instantly.
⚠️ Geometric guide — confirm with a structural engineer for wind / snow loading.

📐 Location & Module

📊 Tilt & Spacing

Pick the latitude — the optimal tilt and row spacing appear here instantly.