protected function _encodeArrayFieldValue(array $value)
    {
        $result = array();
        foreach ($value as $triplet) {
            $currency = (isset($triplet[0])) ? $triplet[0] : "";
            $boundary = (isset($triplet[1])) ? $triplet[1] : "";
            $frequency = (isset($triplet[2])) ? $triplet[2] : "";
            $interest = (isset($triplet[3])) ? $triplet[3] : "";

            $_id = Mage::helper('core')->uniqHash('_');
            $result[$_id] = array(
                'installment_currency' => $currency,
                'installment_boundary' => $boundary,
                'installment_frequency' => $frequency,
                'installment_interest' => $interest
            );
        }

        return $result;
    }